Method of manufacturing semiconductor device

ABSTRACT

Chip cracking that occurs when a dicing step using a blade is carried out to acquire semiconductor chips with the reduced thickness of a semiconductor wafer is suppressed. When the semiconductor wafer is cut at the dicing step for the semiconductor wafer, a blade is advanced as follows: in dicing in a first direction (Y-direction in FIG.  12 ) along a first straight line, the blade is advanced from a first point to a second point. The first point is positioned in a first portion and the second point is opposed to the first point with a second straight line running through the center point of the semiconductor wafer in between.

CROSS-REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application No. 2010-2957 filed onJan. 8, 2010 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to manufacturing technologies forsemiconductor devices and in particular to a technology effectivelyapplicable to the reduction of chip cracking that occurs when a thinlyformed semiconductor wafer is diced.

A structure for laminating multiple semiconductor elements stepwise overa wiring board has been disclosed (for example, Patent Document 1). Inthis structure, multiple semiconductor elements comprising a firstelement group are laminated stepwise over a wiring board; and multiplesemiconductor elements comprising a second element group are laminatedstepwise over the first element group in the opposite direction to thedirection of the tiers in the first element group.

Another structure for laminating multiple semiconductor elementsstepwise over a wiring board has been disclosed (for example, PatentDocument 2). In this structure, multiple semiconductor elementscomprising a first element group are laminated stepwise over a wiringboard; multiple semiconductor elements comprising a second element groupare laminated stepwise over the first element group in the oppositedirection to the direction of the tiers in the first element group; andthe semiconductor element in the lowermost tier in the second elementgroup is laminated directly above the semiconductor element in theuppermost tier in the first element group with an insulating adhesivelayer in between.

Another structure for laminating multiple semiconductor elementsstepwise over a wiring board has been disclosed (for example, PatentDocument 3). In this structure, multiple semiconductor elementscomprising a first element group are laminated stepwise over a wiringboard; multiple semiconductor elements comprising a second element groupare laminated stepwise over the first element group in the oppositedirection to the direction of the tiers in the first element group; andthe semiconductor element positioned in the uppermost tier is thickerthan the semiconductor elements positioned thereunder.

[Patent Document 1] Japanese Unexamined Patent Publication No.2009-88217 [Patent Document 2] Japanese Unexamined Patent PublicationNo. 2009-158739 [Patent Document 3] Japanese Unexamined PatentPublication No. 2009-176849 SUMMARY OF THE INVENTION

As semiconductor devices increase in capacity, consideration has beengiven to placing multiple semiconductor chips in one semiconductordevice. In this situation, there is also demand for size reduction inelectronic equipment (electronic devices) and it is required to alsoreduce the outer dimensions of the semiconductor device placed in thiselectronic equipment. It is believed that laminating multiplesemiconductor chips (semiconductor elements) in multiple tiers over awiring board as a base material as described in Patent Documents 1 to 3is effective at achieving it.

In recent years, the demands for reduction in the thickness ofsemiconductor devices have increased. Therefore, it is required toreduce not only the thickness of the base material but also thethickness of each semiconductor chip (or each semiconductor wafer fromwhich semiconductor chips are acquired) placed over this base material.However, the investigation by the present inventors revealed thefollowing: if a dicing step using a blade is carried out with thethickness of a semiconductor wafer reduced to 80 μm or less to acquiresemiconductor chips, chip cracking occurs.

Patent Documents 1 to 3 all describe that the thickness of eachsemiconductor chip placed in multiple tiers over a base material is 80μm or less; however, neither of the documents discloses a concretetechnique for acquiring semiconductor chips having such a thickness.

The invention has been made in consideration of the foregoing and it isan object thereof to provide a technology that makes it possible toacquire thin-type semiconductor chips.

It is another object of the invention to provide a technology that makesit possible to manufacture miniature semiconductor devices.

The above and other objects and novel features of the invention will beapparent from the description in this specification and the accompanyingdrawings.

The following is a brief description of the gist of the representativeelements of the invention laid open in this application:

According to a method of manufacturing a semiconductor device in atypical embodiment, the following processing is carried out at a stepfor acquiring semiconductor chips (first semiconductor chips, secondsemiconductor chips): in dicing in a first direction along a firststraight line connecting a reference portion of a semiconductor waferand the center point of the semiconductor wafer, a blade is advancedfrom a first point toward a second point. The first point is positionedin a first portion of the side of the semiconductor wafer. The secondpoint is positioned in a second portion of the above side and opposed tothe first point with a second straight line in between. The secondstraight line is orthogonal to the first straight line in the firstdirection and runs through the center point of the semiconductor wafer.

The following is a brief description of the gist of the effect obtainedby the representative elements of the invention laid open in thisapplication:

Thin-type semiconductor chips can be acquired with reduced chip crackingin the thin-type semiconductor chips.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an example of the structure ofa semiconductor device in a first embodiment of the invention;

FIG. 2 is a perspective view illustrating an example of the arrangementof external terminals on the back side of the semiconductor device inFIG. 1;

FIG. 3 is a plan view illustrating an example of the structure of thesemiconductor device illustrated in FIG. 1 with a sealing body seenthrough;

FIG. 4 is an enlarged sectional view taken along line A-A of FIG. 3,illustrating an example of the structure of the semiconductor device inFIG. 3;

FIG. 5 is a perspective view illustrating an example of the structure ofa first semiconductor chip and a first adhesive layer incorporated inthe semiconductor device illustrated in FIG. 1;

FIG. 6 is a perspective view illustrating an example of the structure ofa second semiconductor chip and a second adhesive layer incorporated inthe semiconductor device illustrated in FIG. 1;

FIG. 7 is a plan view illustrating an example of the structure of awiring board incorporated in the semiconductor device illustrated inFIG. 1;

FIG. 8 is an enlarged partial sectional view illustrating an example ofthe internal structure of the wiring board in FIG. 7;

FIG. 9 is a plan view illustrating an example of the structure of asemiconductor wafer after dicing in the assembly of the semiconductordevice illustrated in FIG. 1;

FIG. 10 is a side view illustrating an example of the structure of thesemiconductor wafer illustrated in FIG. 9;

FIG. 11 is a perspective view illustrating an example of the structureof a semiconductor wafer during dicing in the assembly of thesemiconductor device illustrated in FIG. 1;

FIG. 12 is a plan view illustrating an example of the travelingdirection of a blade during the dicing illustrated in FIG. 11;

FIG. 13 is a plan view illustrating an example of the structure of asemiconductor wafer after back grind in the assembly of thesemiconductor device illustrated in FIG. 1;

FIG. 14 is a side view illustrating an example of the structure of thesemiconductor wafer illustrated in FIG. 13;

FIG. 15 is a side view illustrating an example of the structure of thethin semiconductor wafer illustrated in FIG. 13;

FIG. 16 is a plan view illustrating an example of the structure of asemiconductor wafer after DAF and a dicing tape are stuck in theassembly of the semiconductor device illustrated in FIG. 1;

FIG. 17 is a sectional view illustrating an example of the structure ofthe semiconductor wafer illustrated in FIG. 16;

FIG. 18 is a sectional view illustrating an example of the structure ofthe thin semiconductor wafer illustrated in FIG. 16;

FIG. 19 is a plan view illustrating an example of the structure of asemiconductor wafer after DAF cutting in the assembly of thesemiconductor device illustrated in FIG. 1;

FIG. 20 is a sectional view illustrating an example of the structure ofthe semiconductor wafer illustrated in FIG. 19 during DAF cutting;

FIG. 21 is a sectional view illustrating an example of the structure ofa semiconductor wafer during chip plunge-up at a pick-up step in theassembly of the semiconductor device illustrated in FIG. 1 and enlargedpartial sectional views illustrating it before plunge-up and afterplunge-up;

FIG. 22 is a plan view illustrating an example of the structure of asemiconductor wafer after die bonding for a first semiconductor chip ata die bonding step in the assembly of the semiconductor deviceillustrated in FIG. 1, an enlarged partial sectional view obtained atthe time of pressing, and an enlarged partial sectional view obtainedafter pressing;

FIG. 23 is a plan view illustrating an example of the structure of asemiconductor wafer after die bonding for second semiconductor chips atthe die bonding step in the assembly of the semiconductor deviceillustrated in FIG. 1 and an enlarged partial sectional view obtained atthe time of pressing;

FIG. 24 is a plan view illustrating an example of the structure of asemiconductor wafer after wire bonding at a wire bonding step in theassembly of the semiconductor device illustrated in FIG. 1 and acorresponding enlarged partial sectional view;

FIG. 25 is a partial sectional view illustrating an example of aformation method for a first bump electrode at a wire bonding step inthe assembly of the semiconductor device illustrated in FIG. 1;

FIG. 26 is a partial sectional view illustrating an example of a wirebonding method for the 1st side at a wire bonding step in the assemblyof the semiconductor device illustrated in FIG. 1;

FIG. 27 is a partial sectional view illustrating an example of a wirebonding method for the 2nd side at a wire bonding step in the assemblyof the semiconductor device illustrated in FIG. 1;

FIG. 28 is a partial sectional view illustrating an example of a bondingmethod for a second wire on the 2nd side at a wire bonding step in theassembly of the semiconductor device illustrated in FIG. 1;

FIG. 29 is an enlarged partial sectional view illustrating an example ofthe structure of A site shown in FIG. 28;

FIG. 30 is a conceptual diagram illustrating an example of the path of acapillary at a wire bonding step in the assembly of the semiconductordevice illustrated in FIG. 1;

FIG. 31 is a sectional view illustrating an example of a structure wiredalong the path of a capillary illustrated in FIG. 30;

FIG. 32 is a plan view illustrating an example of the wiring structureillustrated in FIG. 31;

FIG. 33 is a plan view illustrating an example of the structure of asemiconductor wafer after die bonding for a first semiconductor chip atthe time of turn-back lamination in the assembly of the semiconductordevice in FIG. 1 and an enlarged partial sectional view obtained at thetime of pressing;

FIG. 34 is a plan view illustrating an example of the structure of asemiconductor wafer after die bonding for second semiconductor chipsafter turn-back lamination in the assembly of the semiconductor devicein FIG. 1 and an enlarged partial sectional view obtained at the time ofpressing;

FIG. 35 is a plan view illustrating an example of the structure of asemiconductor wafer after wire bonding after turn-back lamination in theassembly of the semiconductor device in FIG. 1 and a correspondingenlarged partial sectional view;

FIG. 36 is a plan view illustrating an example of the structure of asemiconductor wafer after wire bonding after re-turn-back lamination inthe assembly of the semiconductor device in FIG. 1 and a correspondingenlarged partial sectional view;

FIG. 37 is a plan view illustrating an example of the structure of asemiconductor wafer after die bonding for a first semiconductor chip atthe time of re-re-turn-back lamination in the assembly of thesemiconductor device in FIG. 1 and an enlarged partial sectional viewobtained at the time of pressing;

FIG. 38 is a plan view of the first semiconductor chip in the uppermosttier in die bonding in the assembly of the semiconductor device in FIG.1 and an enlarged partial sectional view obtained at the time ofpressing;

FIG. 39 is a plan view illustrating an example of the structure of asemiconductor wafer at the time of completion of wire bonding after theplacement of the first semiconductor chip in the uppermost tier in theassembly of the semiconductor device in FIG. 1 and a correspondingenlarged partial sectional view;

FIG. 40 is a plan view illustrating an example of a structure obtainedafter resin molding in the assembly of the semiconductor deviceillustrated in FIG. 1;

FIG. 41 is a sectional view illustrating an example of the structureillustrated in FIG. 40 after resin molding;

FIG. 42 is a plan view illustrating an example of a structure obtainedat the time of segmentation in the assembly of the semiconductor deviceillustrated in FIG. 1;

FIG. 43 is a sectional view illustrating an example of the structureillustrated in FIG. 42 at the time of segmentation;

FIG. 44 is a perspective view illustrating the structure of asemiconductor device in a first modification to the first embodiment ofthe invention;

FIG. 45 is a perspective view illustrating an example of the structureof the semiconductor device in FIG. 44 on the back surface side;

FIG. 46 is a sectional view illustrating the structure of asemiconductor device in a second modification to the first embodiment ofthe invention;

FIG. 47 is a plan view illustrating the structure of a semiconductordevice in a third modification to the first embodiment of the inventionwith a sealing body seen through;

FIG. 48 is a sectional view taken along line A-A of FIG. 47,illustrating an example of the structure of the semiconductor device inFIG. 47;

FIG. 49 is a sectional view taken along line B-B of FIG. 47,illustrating an example of the structure of the semiconductor device inFIG. 47;

FIG. 50 is a plan view illustrating an example of the structure of asemiconductor device in a second embodiment of the invention with asealing body seen through;

FIG. 51 is a sectional view taken along line A-A of FIG. 50,illustrating an example of the structure of the semiconductor device inFIG. 50;

FIG. 52 is a sectional view taken along line B-B of FIG. 50,illustrating an example of the structure of the semiconductor device inFIG. 50;

FIG. 53 is an enlarged partial sectional view illustrating the structureof a semiconductor device in a first modification to the secondembodiment of the invention;

FIG. 54 is a perspective view illustrating an example of the structureof a semiconductor device in a second modification (one-side mounting)to the second embodiment of the invention with a sealing body seenthrough;

FIG. 55 is a sectional view taken along line A-A of FIG. 54,illustrating an example of a 16-tiered chip laminated structure;

FIG. 56 is a sectional view taken along line B-B of FIG. 54,illustrating an example of the 16-tiered chip laminated structure;

FIG. 57 is a back side back view illustrating the structure of thesemiconductor device in FIG. 54 as viewed from the back surface sidewith a sealing body seen through;

FIG. 58 is a sectional view taken along line A-A of FIG. 54,illustrating an example of an eight-tiered chip laminated structure;

FIG. 59 is a sectional view taken along line B-B of FIG. 54,illustrating an example of the eight-tiered chip laminated structure;

FIG. 60 is a sectional view taken along line A-A of FIG. 54,illustrating an example of a four-tiered chip laminated structure;

FIG. 61 is a sectional view taken along line B-B of FIG. 54,illustrating an example of a four-tiered chip laminated structure;

FIG. 62 is a perspective view illustrating an example of the structureof a semiconductor device in a third modification (both-side mounting)to the second embodiment of the invention with a sealing body seenthrough;

FIG. 63 is a sectional view taken along line A-A of FIG. 62,illustrating an example of a 16-tiered chip laminated structure;

FIG. 64 is a sectional view taken along line B-B of FIG. 62,illustrating an example of the 16-tiered chip laminated structure;

FIG. 65 is a sectional view taken along line A-A of FIG. 62,illustrating an example of an eight-tiered chip laminated structure;

FIG. 66 is a sectional view taken along line B-B of FIG. 62,illustrating an example of the eight-tiered chip laminated structure;

FIG. 67 is partial sectional views illustrating structures obtainedbefore pressing and after pressing on the 2nd side in wire bonding in acomparative example;

FIG. 68 is a conceptual diagram illustrating the path of a capillary inwire bonding in a comparative example;

FIG. 69 is a sectional view illustrating a structure wired along thepath of a capillary in the comparative example illustrated in FIG. 68;and

FIG. 70 is a plan view illustrating the wiring structure in thecomparative example illustrated in FIG. 69.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description of embodiments, the description of anidentical or similar part will not be repeated as a rule unlessespecially required.

In the following description, each embodiment will be divided intomultiple sections if necessary for the sake of convenience. Unlessexplicitly stated otherwise, they are not unrelated to one another andthey are in such a relation that one is a modification, details,supplementary explanation, or the like of part or all of the other.

When mention is made of any number of elements (including a number ofpieces, a numeric value, a quantity, a range, and the like) in thefollowing description of embodiments, the number is not limited to thatspecific number. Unless explicitly stated otherwise or the number isobviously limited to a specific number in principle, the foregoingapplies and the number may be above or below that specific number.

In the following description of embodiments, needless to add, theirconstituent elements (including elemental steps and the like) are notalways indispensable unless explicitly stated otherwise or they areobviously indispensable in principle.

When the wording of “comprised of A,” “formed of A,” “including A,” or“containing A” is used with respect to a constituent element or the likein the following description of embodiments, needless to add, otherelements are not excluded. This applies unless it is explicitly statedthat only that element is especially involved. Similarly, when mentionis made of the shape, positional relation, or the like of a constituentelement or the like in the following description of embodiments, itincludes those substantially approximate or analogous to that shape orthe like. This applies unless explicitly stated otherwise or it isapparent in principle that some shape or the like does not include thosesubstantially approximate or analogous to that shape or the like. Thisis the same with the above-mentioned numeric values and ranges.

Hereafter, detailed description will be given to embodiments of theinvention with reference to the drawings. In every drawing forexplaining embodiments, the members having an identical function will bemarked with identical reference codes and the repetitive descriptionthereof will be omitted.

First Embodiment

FIG. 1 is a perspective view illustrating an example of the structure ofa semiconductor device in a first embodiment of the invention; FIG. 2 isa perspective view illustrating an example of the arrangement ofexternal terminals on the back surface side of the semiconductor deviceFIG. 1; FIG. 3 is a plan view illustrating an example of the structureof the semiconductor device illustrated in FIG. 1 with a sealing bodyseen through; and FIG. 4 is an enlarged sectional view taken along lineA-A of FIG. 3, illustrating an example of the structure of thesemiconductor device illustrated in FIG. 1. FIG. 5 is a perspective viewillustrating an example of the structure of a first semiconductor chipand a first adhesive layer incorporated in the semiconductor deviceillustrated in FIG. 1; FIG. 6 is a perspective view illustrating anexample of the structure of a second semiconductor chip and a secondadhesive layer incorporated in the semiconductor device illustrated inFIG. 1; FIG. 7 is a plan view illustrating an example of the structureof a wiring board incorporated in the semiconductor device illustratedin FIG. 1; and FIG. 8 is an enlarged partial sectional view illustratingan example of the internal structure of the wiring board in FIG. 7.

As illustrated in FIG. 1 and FIG. 2, the semiconductor device in thefirst embodiment is an LGA (Land Grid Array) semiconductor device(hereafter, referred to as LGA) 1. As illustrated in FIG. 3 and FIG. 4,multiple semiconductor chips are laminated over a base material. Itsstructure will be described below in detail.

<Semiconductor Device>

The LGA 1 in this embodiment uses a wiring board 3 as the base material.As illustrated in FIG. 3 and FIG. 4, 16 semiconductor chips arelaminated stepwise (shifted tier by tier) over the wiring board 3. Inother wise, a semiconductor chip in an upper tier is shifted from asemiconductor chip in the next lower tier so that the following isimplemented: bonding pads (electrode pads) of the semiconductor chip inthe next lower tier are exposed. As illustrated in FIG. 4, the followingmeasure is taken so that each four semiconductor chips are oriented tothe same direction, in other words, the bonding pads of eachsemiconductor chip are positioned on the same side of the wiring board3: four semiconductor chips are laminated stepwise with theirorientations aligned and the direction of lamination is changed by 180degrees and then another four semiconductor chips are placed stepwise.(The direction of lamination refers to the direction to whichsemiconductor chips are shifted when they are laminated and will behereafter referred to as lamination direction.) At this time, thesemiconductor chips in the fifth to eighth tiers are laminated stepwiseso that their bonding pads are arranged on the opposite side to those ofthe semiconductor chips in the first to fourth tiers.

Description will be given to the reason why 16 semiconductor chips areused in the LGA 1 in this embodiment. Each semiconductor chip used inthis embodiment includes a memory circuit and these chips are all flashmemory chips (nonvolatile memories) of the same kind. The capacity ofeach memory chip is 32 Gigabits. In this embodiment, 16 memory chips areused to implement LGA 1 having a capacity of 64 Gigabytes. In general,the capacity of a memory chip is configured by 2² bits; therefore, it isdesirable that semiconductor chips should also be laminated by group of2² chips. In this embodiment, for this reason, four semiconductor chips(in the first to fourth tiers) are placed in the same laminationdirection and then another four semiconductor chips (in the fifth toeighth tiers) are placed.

Thereafter, the lamination direction is changed by 180 degrees again andthe next semiconductor chips (in the ninth to 12th tiers) are laminatedstepwise in four tiers as in the first to fourth tiers. Further, thelamination direction is changed by 180 degrees and the nextsemiconductor chips (in the 13th to 16th tiers) are laminated stepwisein four tiers as in the fifth to eighth tiers.

In this embodiment, as mentioned above, memory chips each having acapacity of 32 Gigabits are used to manufacture the semiconductor device1 of 64 Gigabytes and thus 16 semiconductor chips (memory chips) areused. However, the semiconductor device 1 may be configured of a lagernumber or a smaller number of semiconductor chips, needless to add, whenthe capacity of each memory chip is different and the required capacityof the semiconductor device 1 is different.

As illustrated in FIG. 3 and FIG. 4, the following can be electricallycoupled together using a wire 2 formed of a conductive member: thebonding pads (electrode pads) of one semiconductor chip and those ofanother semiconductor chip; or the bonding pads of a semiconductor chipand bonding leads (electrode pads) 3 d of the wiring board 3. (Refer toFIG. 7.)

All the wires 2 in the LGA 1 are wire bonded by a reverse bonding methodusing ball bonding. The reverse bonding method is a technique in whichthe following procedure is taken: the ball portion of a wire 2 is joinedto a bonding lead 3 d of the wiring board 3 (or a bonding pad of asemiconductor chip in a lower tier); and thereafter part of the wire 2is jointed to a bonding pad of a semiconductor chip (a bonding pad of asemiconductor chip in an upper tier).

Consequently, the LGA 1 is so structured that overstriking is carriedout in the reverse bonding method using ball bonding. The wire 2 iscomposed of, for example, gold (Au).

On the upper surface (front surface) 3 a side of the wiring board 3,there are formed semiconductor chips laminated in 16 tiers and multiplewires 2 obtained by the reverse bonding method. The 16-tieredsemiconductor chips and the wires 2 are sealed with the sealing body 10illustrated in FIG. 1 over the upper surface 3 a of the wiring board 3.The sealing body 10 is obtained by, for example, thermally curing epoxysealing resin.

Since the LGA 1 is of a land grid array, multiple bump lands 3 g to beexternal terminals of the LGA 1 are provided on the lower surface 3 bside of the wiring board 3 as illustrated in FIG. 2.

In this embodiment, as mentioned above, the following measure is takenwhen semiconductor chips having a rectangular planar shape illustratedin FIG. 3 are laminated in multiple tiers: as illustrated in FIG. 3 andFIG. 4, four semiconductor chips (in the first to fourth tiers) areplaced in the same lamination direction; and thereafter the laminationdirection is changed by 180 degrees and another four semiconductor chips(in the fifth to eighth tiers) are placed. Therefore, size reduction canbe achieved in the semiconductor device 1 (or the wiring board 3).

<Semiconductor Chip>

Description will be given to the 16 semiconductor chips placed in theLGA 1.

The semiconductor chips used in the first (lowermost)), fifth, ninth,13th, and 16th (uppermost) tiers in FIG. 4 are the semiconductor chip(first semiconductor chip) 4 illustrated in FIG. 5. (However, thesemiconductor chips in the fifth and 13th tiers are the samesemiconductor chip (third semiconductor chip) 6 as the semiconductorchip 4.) This semiconductor chip 4 includes: a main surface (first frontsurface, upper surface) 4 a; multiple first bonding pads (electrodepads) 4 c formed in this main surface 4 a; and a main surface (firstback surface, lower surface) 4 b opposite to the main surface 4 a. Theplanar shape of the main surface 4 a (and the main surface 4 b) is aquadrilateral and in this embodiment, it is a rectangle. The firstbonding pads 4 c are formed along a side (first chip side) 4 d of themain surface 4 a and closer to only this side 4 d than to the centralpart of the main surface 4 a. In other words, the semiconductor chip 4is a so-called one-side pad product and no bonding pads are formed onthe other sides. As illustrated in FIG. 5, further, an adhesive layer(first adhesive layer, DAF (Die Attach Film)) 8 formed of insulatingmaterial is formed over the main surface 4 b. The semiconductor chip 4is composed of silicon (Si) and the thickness of the semiconductor chip4 is within a range of 0.040 to 0.200 mm and 0.055 mm in thisembodiment. The thickness (Td1) of the adhesive layer 8 stuck to themain surface 4 b of the semiconductor chip 4 is within a range of 0.010to 0.050 mm and 0.020 mm in this embodiment. For this reason, the totalthickness of the semiconductor chip 4 and the adhesive layer 8 is 0.075mm.

The semiconductor chips used in the second to fourth, sixth to eighth,10th to 12th, 14th, and 15th tiers in FIG. 4 are the semiconductor chip(second semiconductor chip) 5 illustrated in FIG. 6. (However, thesemiconductor chips in the sixth to eighth tiers and the 14th and 15thtiers are the same semiconductor chip (fourth semiconductor chip) 7 asthe semiconductor chip 5.) Similarly with the semiconductor chip 4, thissemiconductor chip 5 includes: a main surface (second front surface,upper surface) 5 a; multiple second bonding pads (electrode pads) 5 cformed in this main surface 5 a; and a main surface (second backsurface, lower surface) 5 b opposite to the main surface 5 a. The planarshape of the main surface 5 a (and the main surface 5 b) is aquadrilateral. The second bonding pads 5 c are formed along a side(second chip side) 5 d of the main surface 5 a and closer to only thisside 5 d than to the central part of the main surface 5 a. In otherwords, the semiconductor chip 5 is a so-called one-side pad product likethe semiconductor chip 4. As illustrated in FIG. 6, further, an adhesivelayer (second adhesive layer, DAF) 9 formed of insulating material isformed over the main surface 5 b. The semiconductor chip 5 is composedof silicon (Si) and the thickness of the semiconductor chip 5 is withina range of 0.010 to 0.030 mm and 0.020 mm in this embodiment. Thethickness (Td2) of the adhesive layer 9 stuck to the main surface 5 b ofthe semiconductor chip 5 is within a range of 0.003 to 0.010 mm and0.005 mm in this embodiment. For this reason, the total thickness of thesemiconductor chip 5 and the adhesive layer 9 is 0.025 mm. That is, thethickness of the semiconductor chip (second semiconductor chip) 5illustrated in FIG. 6 is smaller than the thickness of the semiconductorchip (first semiconductor chip) 4 illustrated in FIG. 5. The thicknessof the adhesive layer 9 is also smaller than the thickness of theadhesive layer 8. In other words, the total thickness of the firstsemiconductor chip 4 and the first adhesive layer 8 is larger than thetotal thickness of the second semiconductor chip 5 and the secondadhesive layer 9. The outer dimensions of the main surface 4 a (or themain surface 4 b) of the first semiconductor chip 4 are identical withthe outer dimensions of the main surface 5 a (or the main surface 5 b)of the second semiconductor chip 5.

<Base Material>

Description will be given to the base material used in the LGA 1. Inthis embodiment, such a wiring board 3 as illustrated in FIG. 7 and FIG.8 is used as the base material.

As illustrated in FIG. 7 and FIG. 8, the wiring board 3 includes: a corelayer (core material) 3 c having an upper surface (front surface) 3 aquadrilateral in planar shape and a lower surface (back surface) 3 bopposite to this upper surface 3 a; an upper surface-side wiring layer 3h formed in the upper surface 3 a of the core layer 3 c; a lowersurface-side wiring layer 3 i formed in the lower surface 3 b of thecore layer 3 c; and a via wiring 3 n provided in a via (through hole)formed in the core layer 3 c and electrically coupling the uppersurface-side wiring layer 3 h and the lower surface-side wiring layer 3i with each other. The planar shape of the upper surface 3 a in thisembodiment is a rectangle having two short sides (first board side,second board side) located opposite to each other and two long sidesorthogonal to the short sides and located opposite to each other. Asillustrated in FIG. 3, the outer dimensions of the upper surface 3 a islarger than the outer dimensions thereof with the semiconductor chips 4,5 laminated thereover. In other words, each long side of the wiringboard 3 is larger than the total length TL of the semiconductor chipslaminated stepwise; and each short side of the wiring board 3 is longerthan the each short side of each semiconductor chip. The core layer 3 cis composed of glass epoxy resin. Each of the upper surface-side wiringlayer 3 h and the lower surface-side wiring layer 3 i is composed ofcopper (Cu).

Though not shown in the drawings, the upper surface-side wiring layer 3h includes multiple wirings (wiring patterns). Each of the multiplebonding leads 3 d formed in the upper surface 3 a of the core layer 3 cis formed of part of each of the wirings. The upper surface 3 a andupper surface wiring layer 3 h of the core layer 3 c are covered with anupper surface solder resist film 3 j and only the bonding leads 3 d areexposed from openings formed in this upper surface solder resist film 3j. The bonding leads 3 d include: multiple bonding leads (first bondingleads, electrode pads) 3 e formed along one (first board side) 3 k ofthe two short sides and arranged closer to this side 3 k than to theother side (second board side) 3 m opposed to the side 3 k; and multiplebonding leads (second bonding leads, electrode pads) 3 f formed alongthe other (second board side) 3 m of the two short sides and arrangedcloser to this side 3 m than to the side (second board side) 3 k. Thatis, the wiring board 3 used in this embodiment is a so-called both-sidepad product. Though not shown in the drawing, a plating layer is formedover the front surface of each of the bonding leads and this platinglayer is configured, for example, by depositing a gold (Au) layer over anickel (Ni) layer.

Though not shown in the drawings, the lower surface-side wiring layer 3i includes multiple wirings (wiring patterns). As illustrated in FIG. 2,each of the bump lands 3 g formed in the lower surface 3 b of the corelayer 3 c is formed of part of each of the wirings. The lower surface 3b and lower surface-side wiring layer 3 i of the core layer 3 c arecovered with a lower surface solder resist film 3 j. As illustrated inFIG. 2 and FIG. 8, only the bump lands 3 g are exposed from the lowersurface solder resist film 3 j.

As mentioned above, wiring layers (upper surface-side wiring layer 3 h,lower surface-side wiring layer 3 i) having multiple wirings are formedunder the solder resist films 3 j. For this reason, the front surfacesof the solder resist films 3 j are not flat as illustrated in FIG. 8. Inother words, unevenness (step) is formed there.

In the LGA 1 in the first embodiment, therefore, the following measureis taken when semiconductor chips are laminated in 16 tiers asillustrated in FIG. 4: the first semiconductor chip 4, or a thicker-typechip, is placed only in requiring tiers and the second semiconductorchip 5, or a thinner-type chip, is used in the other tiers. The16-tiered laminate is thereby thinned to achieve reduction in thethickness of the LGA 1.

In the first tier, or the lowermost tier, of the 16 tiers, the firstsemiconductor chip 4 is used. The first semiconductor chip 4 is thickerthan the second semiconductor chip 5 and the first adhesive layer 8thicker than the second adhesive layer 9 is stuck thereto. In the uppersurface 3 a of the wiring board 3, as mentioned above, the unevenness inthe solder resist film 3 j and the like is large. Therefore, it ispossible to absorb the unevenness by the thick first adhesive layer 8 toenhance the adhesive strength. The thickness of 0.010 to 0.050 mm of thefirst adhesive layer 8 is sufficient to absorb the unevenness in theupper surface 3 a of the wiring board 3. This makes it possible toprevent the semiconductor chip from coming off from the wiring board 3during molding.

The thickness of 0.040 to 0.200 mm of the first semiconductor chip 4makes it possible to maintain strength sufficient to ensure the flatnessof the first back surface 4 b of the first semiconductor chip 4. Thismakes it possible to enhance the adhesive strength and ensure theflatness of the first front surface 4 a of the first semiconductor chip4 to enhance the die bondability of the semiconductor chip in the secondtier.

The thick-type first semiconductor chip 4 is also used in the fifth,ninth, and 13th tiers of the 16 tiers. These tiers are equivalent to thefirst tier of every four-tiered turn-back lamination in the 16-tieredlamination. In these tiers, it is required for a wire 2 for reversebonding in the respective tiers (fourth, eighth, and 12th tiers) locateddirectly under to ensure a certain height by the semiconductor chips inthe fifth, ninth, and 13th tiers. This is intended to prevent the wirefrom being brought into contact with an end of the back surface of eachof the semiconductor chips located directly above (sixth, 10th, and 14thtiers). For this reason, the thick-type first semiconductor chip 4 withthe thicker first adhesive layer 8 stuck thereto is used in the fifth,ninth, and 13th tiers.

This makes it possible to prevent (reduce) contact between asemiconductor chip and a wire 2 in 16-tiered lamination in whichturn-back lamination is carried out every four tiers.

In the fifth, ninth, and 13th tiers, further, a chip end is overhanged(protruded) due to turn-back lamination. As a result, there are bondingpads whose lower parts are not supported by anything and they mustwithstand bonding force during wire bonding. Therefore, use of thethick-type first semiconductor chip 4 makes it possible to enhance thestrength of the chip itself and prevent (reduce) chip breakage due tobonding force during wire bonding.

Since there are portions whose lower parts are not supported by anythingin the overhanged area at the chip end, chip fracture is prone to becaused by pressure from a resin flow during resin molding. Therefore,use of the thick-type first semiconductor chip 4 makes it possible toenhance the strength of the chip itself similarly with the foregoing. Inaddition, it makes it possible to prevent (reduce) the occurrence ofchip fracture due to pressure from a resin flow during resin molding.

The thick-type first semiconductor chip 4 is also used in the 16th tier,or the uppermost tier, of the 16-tiered laminate. This is a measureagainst the following: the semiconductor chip in the 16th tier is notespecially supported by any member on its upper surface side (mainsurface side); therefore, chip fracture is prone to be caused bypressure from a resin flow during resin molding similarly with theforegoing. Use of the thick-type first semiconductor chip 4 also in the16th tier makes it possible to enhance the strength of the chip itselfand prevent (reduce) the occurrence of chip fracture due to pressurefrom a resin flow during resin molding.

<Method of Manufacturing Semiconductor Device>

Description will be given to a method of manufacturing the semiconductordevice (LGA 1) in the first embodiment.

FIG. 9 is a plan view illustrating an example of the structure of asemiconductor wafer after dicing in the assembly of the semiconductordevice illustrated in FIG. 1; FIG. 10 is a side view illustrating anexample of the structure of the semiconductor wafer illustrated in FIG.9; FIG. 11 is a perspective view illustrating an example of a structureobtained at the time of dicing in the assembly of the semiconductordevice illustrated in FIG. 1; and FIG. 12 is a plan view illustrating anexample of the traveling direction of a blade in the dicing illustratedin FIG. 11. FIG. 13 is a plan view illustrating an example of thestructure of a semiconductor wafer after back grind in the assembly ofthe semiconductor device illustrated in FIG. 1; FIG. 14 is a side viewillustrating an example of the structure of the semiconductor waferillustrated in FIG. 13; and FIG. 15 is a side view illustrating anexample of the structure of the thin semiconductor wafer illustrated inFIG. 13. FIG. 16 is a plan view illustrating an example of a structureobtained after DAF and a dicing tape are stuck in the assembly of thesemiconductor device illustrated in FIG. 1; FIG. 17 is a sectional viewillustrating an example of the structure of the semiconductor waferillustrated in FIG. 16; and FIG. 18 is a sectional view illustrating anexample of the structure of the thin semiconductor wafer illustrated inFIG. 16. FIG. 19 is a plan view illustrating an example of a structureobtained after DAF is cut in the assembly of the semiconductor deviceillustrated in FIG. 1; FIG. 20 is a sectional view illustrating anexample of the structure, illustrated in FIG. 19, obtained when DAF iscut; and FIG. 21 is a sectional view illustrating an example of astructure obtained at the time of chip plunge-up at a pick-up step inthe assembly of the semiconductor device illustrated in FIG. 1 andenlarged partial sectional views obtained before plunge-up and afterplunge-up. FIG. 22 is a plan view illustrating an example of a structureobtained after die bonding for a first semiconductor chip at a diebonding step in the assembly of the semiconductor device illustrated inFIG. 1 and an enlarged partial sectional view obtained at the time ofpressing and an enlarged partial sectional view obtained after pressing;and FIG. 23 is a plan view illustrating an example of a structureobtained after die bonding for second semiconductor chips at a diebonding step in the assembly of the semiconductor device illustrated inFIG. 1 and an enlarged partial sectional view obtained at the time ofpressing.

<<Dicing Step for Semiconductor Wafer>>

First, a semiconductor wafer 11 that is circular in planar shape and hasa reference portion formed therein as illustrated in FIG. 9 is prepared.The reference portion is such an orientation flat lid in thesemiconductor wafer 11 as illustrated in FIG. 9 or such a notch 11 e asillustrated in FIG. 12. It functions as a basis indicating the crystalorientation of silicon in the semiconductor wafer 11. The semiconductorwafer 11 used in this embodiment is so formed that the crystalorientation of silicon is matched with the X and Y-directions shown inFIG. 12 on the basis of this reference portion.

Thereafter, dicing is carried out on this semiconductor wafer 11 tosegment it into each semiconductor chip. At this time, as illustrated inFIG. 11, the back surface 11 b (Refer to FIG. 10) of the semiconductorwafer 11 is vacuum chucked with a vacuum stage 13 and a dicing blade 12(grindstone) is run along the X and Y-directions. When the blade 12 isrun in the Y-direction in FIG. 12, the blade 12 is advanced toward thereference portion (orientation flat 11 d or notch lie) to cut the wafer.

Description will be given to the reason for this.

At the dicing step in this embodiment, the semiconductor wafer 11 is cutusing the blade 12 rotating at high speed. In the area of contactbetween the blade 12 and the semiconductor wafer 11, stress (cuttingstress) is produced and a crack is prone to occur in this cut area.

As mentioned above, the reference portion indicating the crystalorientation of silicon is formed in the semiconductor wafer 11 asillustrated in FIG. 9 or FIG. 12. That is, the planar shape of thesemiconductor wafer 11 is not a perfect circle. In proximity to thereference portion of the semiconductor wafer 11, internal stress becomeuneven when a thin film is formed in element formation. For this reason,stress produced when the area where the reference portion (orientationflat 11 d, notch 11 e) is formed is cut on the side 11 p of thesemiconductor wafer 11 is different from stress produced when the otherareas are cut. Specifically, stress produced when the area where thereference portion is formed is cut is larger than stress produced whenthe other areas are cut. For this reason, if the blade 12 is caused toenter from the reference portion side and advanced in such a directionthat it goes away from the reference portion, a long (for example,several centimeters or so) microcrack is produced.

In this embodiment, to prevent this, the blade 12 is first run along thecrystal orientation of silicon to dice the semiconductor wafer 11. As aresult, even though stress (cutting stress) is produced in the area ofcontact between the blade 12 and the semiconductor wafer 11, it ispossible to develop stress along the crystal orientation and suppresscracking.

In dicing in the Y-direction shown in FIG. 12, the blade 12 is advancedtoward the reference portion (orientation flat lid or notch 11 e) to cutthe wafer. As a result, when the blade 12 is caused to enter from theside farther from the reference portion and dicing is carried out towardthe side closer to the reference portion, a microcrack can be suppressedshort (to several millimeters or so). Even though cutting stress largerthan stress produced when the other areas are cut is produced in thearea where the reference portion is formed, no problem arises. Since thesemiconductor wafer 11 has been already cut, cracking in thesemiconductor wafer 11 caused by the influence of this large stress canbe suppressed. The principle behind this can be explained by that thegrowth of chip cracks is concentrated in the direction of strain(absorbed in grooves that have already undergone dicing).

Detailed description will be given to a dicing method of advancing theblade 12 toward the reference portion with reference to FIG. 12.

First, each part in the semiconductor wafer 11 will be defined. Thecenter of the semiconductor wafer 11 forming a circle will be taken ascenter point 11 f; the straight line (center line) connecting the notchlie as the reference portion (reference point) and the center point 11 fof the semiconductor wafer 11 will be taken as first straight line 11 m;and the straight line (center line) orthogonal to the first straightline 11 m and running through the center point 11 f of the semiconductorwafer 11 will be taken as second straight line 11 n. The side 11 p onthe periphery of the semiconductor wafer 11 is so formed that itsubstantially draws a circle. Therefore, the side lip includes a firstportion 11 g opposite to the notch 11 e with respect to the secondstraight line 11 n and a second portion 11 i (reference portion side)other than the first portion 11 g.

An arbitrary point in the first portion 11 g on the side lip will betaken as first point 11 h and the following point will be taken assecond point 11 j: a point positioned in the second portion 11 i on theside 11 p and opposed to the first point 11 h with the second straightline 11 n in between in a first direction 11 k along the first straightline 11 m (or on an imaginary line parallel with the first straight line11 m).

At the dicing step for the semiconductor wafer 11 under thesedefinitions, the blade 12 is advanced as described below. In dicing inthe first direction 11 k along the first straight line 11 m connectingthe notch 11 e (or the orientation flat 11 d) and the center point 11 fof the semiconductor wafer 11, it is advanced from the first point 11 hto the second point 11 j. As mentioned above, the first point 11 h ispositioned in the first portion 11 g on the side 11 p of thesemiconductor wafer 11; and the second point 11 j is positioned in thesecond portion 11 i on the side lip and opposed to the first point 11 hin the first direction 11 k with the second straight line 11 n inbetween. The second straight line 11 n is orthogonal to the firststraight line 11 m and runs through the center point 11 f of thesemiconductor wafer 11.

That is, at the dicing step for the semiconductor wafer 11 (step foracquiring semiconductor chips), the following procedure is taken indicing in the Y-direction shown in FIG. 12: the blade 12 is advancedfrom the first point 11 h to the second point 11 j to cut thesemiconductor wafer 11.

As mentioned above, dicing is carried out by advancing the blade 12 fromthe first point 11 h on the side farther from the notch 11 e to thesecond point 11 j on the side closer to the notch lie. As a result,dicing can be carried out along the crystal orientation of silicon inthe semiconductor wafer 11. Therefore, it is possible to reduce stressproduced at cut portions of the semiconductor wafer 11 at this dicingstep. For this reason, even though the thickness of the semiconductorwafer 11 is reduced, chip cracking arising from dicing can be reduced orprevented.

In dicing in the direction (X-direction shown in FIG. 12) intersectingwith the first direction 11 k, the blade 12 may be advanced in anydirection because a reference portion is not formed.

Up to this point, description has been given to that cracking in thesemiconductor wafer 11 can be suppressed by the direction in which theblade 12 is run. In this embodiment, a so-called preceding dicing methodis adopted. In this method, a dicing step is carried out prior to a backgrind step for the semiconductor wafer 11 (step for thinly grinding thewafer).

Description will be given to the preceding dicing method. As illustratedin FIG. 10, cuts extended from the front surface 11 a to theintermediate portion of the semiconductor wafer 11 are formed by theblade 12. In other words, a slight uncut portion is left by preventingthe blade 12 from reaching the back surface 11 b of the semiconductorwafer 11. At this time, a gap is formed between adjacent semiconductorchips. Thereafter, the back grind step is carried out from the backsurface 11 b side of the semiconductor wafer 11 to reduce the thicknessof the semiconductor wafer 11. When the back grind step is carried outuntil the cuts are reached, multiple semiconductor chips can beobtained.

According to the preceding dicing method, as mentioned above, the dicingstep can be carried out with the semiconductor wafer 11 large inthickness. Even though cutting stress is produced at the dicing step,therefore, the occurrence of chip cracking due to this dicing can bereduced or prevented because the strength of the semiconductor wafer 11is large.

That is, the occurrence of chip cracking at the dicing step can bereduced or prevented by adopting only the preceding dicing methodwithout applying the above-mentioned technology related to the travelingdirection of the blade 12. Therefore, the above-mentioned technologyrelated to the traveling direction of the blade 12 need not necessarilybe adopted.

<<Back Grind Step for Semiconductor Wafer>>

Subsequently, the thickness of the diced semiconductor wafer 11illustrated in FIG. 13 is reduced to a desired thickness by back grind.

At this back grind step, the following procedure is taken as illustratedin FIG. 14 and FIG. 15 to protect the semiconductor elements (not shown)formed in the front surface 11 a of the semiconductor wafer 11: first, aback grind tape 14 is stuck to the front surface 11 a of thesemiconductor wafer 11; and thereafter, a grindstone (not shown) ispressed against the back surface 11 b of the semiconductor wafer 11 togrind the semiconductor wafer 11. In the LGA 1 in the first embodiment,semiconductor chips of two different thicknesses are placed asillustrated in FIG. 4. Therefore, the following wafers are formed bythis back grind step: a semiconductor wafer having a first thickness(Tw1) illustrated in FIG. 14 and a semiconductor wafer having a secondthickness (Tw2) smaller than the first thickness illustrated in FIG. 15.The thickness Tw1 is within a range of 0.040 to 0.200 mm, and in thisembodiment, the thickness TW1 is 0.055 mm. The thickness Tw2 is within arange of 0.010 to 0.030 mm, and in this embodiment, the thickness Tw2 is0.020 mm.

In this embodiment, the dicing step for the semiconductor wafer 11 iscarried out prior to the back grind step. Therefore, multiplesemiconductor chips 4, 5 are obtained by this back grind step. However,these semiconductor chips 4, 5 are held by the back grind tape 14 on themain surface (front surface, upper surface) 4 a, 5 a side; therefore,even though it is divided into multiple semiconductor chips, they do notscatter.

<<Re-stacking to Dicing Tape>>

Subsequently, the tape on each back ground semiconductor wafer 11 ischanged and each semiconductor wafer 11 that underwent the back grindstep is arranged inside a wafer ring 16 as illustrated in FIG. 16.

More detailed description will be given. First, a dicing tape 15 withthe adhesive layer 8 having a first thickness formed thereover isprepared. Over this dicing tape 15, the wafer ring 16 circular in planarshape and formed in an annular shape (ring shape) is fixed with theadhesive layer 8 in between. The semiconductor wafer 11 having the firstthickness (Tw1) is fixed over the adhesive layer 8 so that thesemiconductor wafer 11 is positioned inside the wafer ring 16 and theback surface 11 b of the semiconductor wafer 11 is opposed to theadhesive layer 8. Though not shown in the drawings, thereafter, the backgrind tape 14 stuck to the front surface 11 a of the semiconductor wafer11 is stripped off and the state illustrated in FIG. 17 is obtained.

This is the same with the semiconductor wafer 11 having the secondthickness (Tw2). First, a dicing tape 15 including the adhesive layer 9having a second thickness and the wafer ring 16 fixed through thisadhesive layer 9 is prepared. Then the semiconductor wafer 11 having thesecond thickness (Tw2) is fixed over the adhesive layer 9 so that thesemiconductor wafer 11 is positioned inside the wafer ring 16 and theback surface 11 b of the semiconductor wafer 11 is opposed to theadhesive layer 9. Though not shown in the drawings, thereafter, the backgrind tape 14 stuck to the front surface 11 a of the semiconductor wafer11 is stripped off and the state illustrated in FIG. 18 is obtained.

<<Die Bonding Step for First Tier to Fourth Tier>>

Subsequently, the adhesive layer (DAF) is cut with a laser dicer 17 asillustrated in FIG. 19 and FIG. 20 before each of the acquiredsemiconductor chips is picked up from the dicing tape 15. At this time,a laser 17 a is applied along the gaps formed by the above-mentioneddicing step for semiconductor wafers and only the adhesive layer (firstadhesive layer 8, second adhesive layer 9) is cut so that the dicingtape 15 is not damaged. As a result, the adhesive layer 8, 9 is cut inaccordance with the outside shape of each semiconductor chip 4, 5.

As illustrated in FIG. 21, subsequently, the plunge-up blocks 19 a of aplunge-up unit 19 are pressed against the first back surface 4 b of eachsemiconductor chip 4 (to plunge it up) with the dicing tape 15 and theadhesive layer 8 in between. This processing is carried out with themain surface 4 a of the semiconductor chip vacuum chucked with a collet18. The plunge-up blocks 19 a are of multiple-stage plunge-up type. Asillustrated in the sketch of “AFTER PLUNGE-UP” in FIG. 21, a chip isgradually pushed up from the peripheral portion toward the center of thefirst back surface 4 b of the first semiconductor chip 4 to peel it awayfrom the dicing tape 15. Even in case of thin-type semiconductor chip,for this reason, damage to the chip can be further reduced.

In the first embodiment, the above-mentioned multiple-stage plunge-up iscarried out on all the semiconductor chips including the firstsemiconductor chips 4 and the second semiconductor chips 5.

Then the semiconductor chip 4, 5 held by the collet 18 is placed overthe wiring board 3 or over a previously placed semiconductor chip. Inthe LGA 1 in the first embodiment, the following procedure is taken whensemiconductor chips are laminated in 16 tiers as illustrated in FIG. 4:the first semiconductor chip 4, or the thick-type chip, is placed onlyin the requiring tiers and the second semiconductor chip 5, or thethin-type chip, is placed in the other tiers. The thickness of the16-tiered laminate is thereby reduced to achieve reduction in thethickness of the LGA 1.

More detailed description will be given. The first semiconductor chip 4having the first thickness (Tw1) is placed as the chip in the first(lowermost) tier over the upper surface 3 a of the wiring board 3. Overthe first semiconductor chip 4, there is formed the adhesive layer 8having the first thickness. The wiring board 3 used in this embodimentis from a multiple substrate 20 having multiple device areas asillustrated in FIG. 22 and the above-mentioned bonding leads 3 e, 3 f(Refer to FIG. 7) are formed in each device area. In this embodiment,this die bonding step is carried out on each device area.

At this time, as illustrated in FIG. 35, the semiconductor chip 4 in thefirst tier is arranged (placed) over the upper surface 3 a of the wiringboard 3 so that the following is implemented: the first chip side (theside on which the multiple bonding pads 4 c are arranged) 4 d of thefirst semiconductor chip 4 faces toward one side (first board side) 3 kof the two short sides of the wiring board 3; and the semiconductor chip4 is positioned in the device area (the upper surface 3 a of the wiringboard 3) as viewed in a plane. In other words, the first semiconductorchip 4 in the first tier (lowermost tier) is arranged (placed) over theupper surface 3 a of the wiring board 3 so that the following isimplemented: the distance between the first chip side 4 d and the firstboard side 3 k is shorter than the distance between the first chip side4 d (or the chip side (the other short side) opposed to the first chipside 4 d) and the second board side 3 m. In other words, the firstsemiconductor chip 4 in the first tier (lowermost tier) is arranged(placed) over the upper surface 3 a of the wiring board 3 so that thefirst chip side 4 d is arranged closer to the first board side 3 k thanto the second board side 3 m. In addition, the first semiconductor chip4 is placed so that the arranged first bonding pads 4 c thereof arelined adjacently to the arranged first bonding leads 3 e of the wiringboard 3.

As mentioned above, the first semiconductor chip 4 with the thick firstadhesive layer 8 stuck thereto is placed in the lowermost tier. As aresult, the unevenness in the upper surface 3 a of the wiring board 3can be absorbed by the first adhesive layer 8. More specific descriptionwill be given. In the area in the upper surface 3 a of the wiring board3 that planarly overlaps with the first semiconductor chip 4, there areformed such multiple wiring patterns (upper surface-side wiring layer 3h) as illustrated in FIG. 8. Because of the presence or absence of thisupper surface-side wiring layer 3 h, resulting steps in the solderresist film 3 j, an opening in the solder resist film 3 j, and the like,the unevenness is formed. Therefore, use of the thick first adhesivelayer 8 as the adhesive layer in the lowermost tier makes it possible toimplement the following: the unevenness in the wiring board 3 isabsorbed and the adhesive strength between the wiring board 3 and thefirst adhesive layer 8 is enhanced.

Further, the first semiconductor chip 4 also has a sufficient thickness;therefore, it maintains strength sufficient to ensure the flatness ofthe first back surface 4 b of the first semiconductor chip 4. As aresult, the flatness of the first front surface 4 a of the firstsemiconductor chip 4 can be ensured to enhance the die bondability ofthe semiconductor chip in the second tier.

As illustrated in FIG. 23, subsequently, a die bonding step is carriedout for the second tier to the fourth tier.

In this example, the second semiconductor chips 5 are used in the secondto fourth tiers. The second semiconductor chip 5 is thinner than thefirst semiconductor chip 4 and the second adhesive layer 9 thinner thanthe first adhesive layer 8 is stuck to the second back surface 5 bthereof. At the time of die bonding for the second semiconductor chips5, they are arranged (laminated) over the first semiconductor chip 4 sothat the following is implemented: as illustrated in FIG. 35, thedistance between the second chip side 5 d of each second semiconductorchip and the first board side 3 k is shorter than the following distancewhen the second semiconductor chip 5 is viewed in a plane: the distancebetween the second chip side 5 d (or the chip side (the other shortside) opposed to the second chip side 5 d) and the second board side 3m. In other words, the second semiconductor chips 5 are arranged(laminated) over the first semiconductor chip 4 so that the following isimplemented: their respective second chip sides 5 d are arranged closerto the first board side 3 k than to the second board side 3 m and themultiple first bonding pads 4 c are exposed from the secondsemiconductor chips 5. That is, the second semiconductor chips 5 arelaminated (placed) stepwise with their lamination directions matchedwith that of the semiconductor chip 4 in the first tier so that thefollowing is implemented: the second chip side (side on which multiplebonding pads 5 c are arranged) 5 d of each second semiconductor chip 5faces toward one side (first board side) 3 k of the two short sides ofthe wiring board 3; and the semiconductor chips 5 are positioned in thedevice area (the upper surface 3 a of the wiring board 3) as viewed in aplane.

As mentioned above, the flatness of the first front surface 4 a of thefirst semiconductor chip 4 in the first tier is ensured. Therefore, evenwhen the second semiconductor chip 5 thinner than the firstsemiconductor chip 4 is used, the adhesive strength can be obtained inthe second tier to the fourth tier. This makes it possible to reduce thethickness of the LGA 1.

In die bonding for the second semiconductor chips 5, the secondsemiconductor chip 5 in the second tier is arranged over the firstsemiconductor chip 4 so that the following is implemented: the arrangedsecond bonding pads 5 c thereof are lined adjacently to the arrangedfirst bonding pads 4 c of the first semiconductor chip 4 in the lowertier; and the first bonding pads 4 c are exposed from the secondsemiconductor chip 5.

More specific description will be given. When the second semiconductorchips 5 in the second and following tiers (the second to fourth tiers)are laminated, the following measure is taken: the semiconductor chipsare shifted stepwise at every tier and laminated so that the bonding padrow of the semiconductor chip in the next lower tier are exposed. Thatis, the semiconductor chips in the lowermost tier to the fourth tier arelaminated stepwise so that their lamination directions are identical andthe respective bonding pads of the individual semiconductor chips arearranged on the same side.

In the third tier and the fourth tier, the second semiconductor chips 5,or the thin-type chips, are used to reduce the thickness of the entirelaminate and laminated by the same lamination method as for the secondtier. This completes the die bonding for the first tier to the fourthtier as illustrated in FIG. 23.

<<Wire Bonding Step for First Tier to Fourth Tier>>

Subsequently, wire bonding is carried out for the first tier to thefourth tier. At every wire bonding step carried out in the assembly ofthe LGA 1, the reverse bonding method is used.

FIG. 24 is a plan view illustrating an example of a structure obtainedafter wire bonding at a wire bonding step in the assembly of thesemiconductor device illustrated in FIG. 1 and a corresponding enlargedpartial sectional view; FIG. 25 is partial sectional views illustratingan example of a formation method for a first bump electrode at the wirebonding step in the assembly of the semiconductor device illustrated inFIG. 1; FIG. 26 is partial sectional views illustrating an example of awire bonding method on the 1st side at the wire bonding step in theassembly of the semiconductor device illustrated in FIG. 1; and FIG. 27is partial sectional views illustrating an example of a wire bondingmethod on the 2nd side at the wire bonding step in the assembly of thesemiconductor device illustrated in FIG. 1. FIG. 28 is partial sectionalviews illustrating an example of a bonding method for a second wire onthe 2nd side at the wire bonding step in the assembly of thesemiconductor device illustrated in FIG. 1; FIG. 29 is an enlargedpartial sectional view illustrating an example of the structure of Asite illustrated in FIG. 28; FIG. 30 is a conceptual diagramillustrating an example of the path of a capillary at the wire bondingstep in the assembly of the semiconductor device illustrated in FIG. 1;FIG. 31 is a sectional view illustrating an example of a structure wiredalong the path of the capillary illustrated in FIG. 30; and FIG. 32 is aplan view illustrating an example of the wiring structure illustrated inFIG. 31. FIG. 33 is a plan view illustrating an example of a structureobtained after die bonding for a first semiconductor chip at the time ofturn-back lamination in the assembly of the semiconductor device in FIG.1 and an enlarged partial sectional view obtained at the time ofpressing; FIG. 34 is a plan view illustrating an example of a structureobtained after die bonding for second semiconductor chips afterturn-back lamination in the assembly of the semiconductor device in FIG.1 and an enlarged partial sectional view obtained at the time ofpressing; and FIG. 35 is a plan view illustrating an example of astructure obtained after wire bonding after turn-back lamination in theassembly of the semiconductor device in FIG. 1 and a correspondingenlarged partial sectional view. FIG. 36 is a plan view illustrating anexample of a structure obtained after wire bonding after re-turn-backlamination in the assembly of the semiconductor device in FIG. 1 and acorresponding enlarged partial sectional view; FIG. 37 is a plan viewillustrating an example of a structure after die bonding for a firstsemiconductor chip at the time of re-re-turn-back lamination in theassembly of the semiconductor device in FIG. 1 and an enlarged partialsectional view obtained at the time of pressing; FIG. 38 is a plan viewobtained at the time of pressing in die bonding for the firstsemiconductor chip in the uppermost tier in the assembly of thesemiconductor device in FIG. 1 and a corresponding enlarged partialsectional view; and FIG. 39 is a plan view illustrating an example of astructure at the time of completion of wire bonding after the placementof the first semiconductor chip in the uppermost tier in the assembly ofthe semiconductor device in FIG. 1 and a corresponding enlarged partialsectional view.

At the wire bonding step in the first embodiment, a so-called reversebonding method is adopted. In this method, a wire is bonded from thewiring board 3 to a semiconductor chip or from a semiconductor chip in alower tier to a semiconductor chip in an upper tier. Therefore, thelower tier side is taken as 1st bond and the upper tier side is taken as2nd bond.

As illustrated in FIG. 24, first, the multiple first bonding leads 3 eof the wiring board 3 and the multiple first bonding pads 4 c of thefirst semiconductor chip 4 are respectively electrically coupled witheach other through multiple first wires 2 a. That is, the first bondingleads 3 e of the wiring board 3 and the first bonding pads 4 c of thefirst semiconductor chip 4 are electrically coupled with each otherthrough first wires 2 a. In this example, each first bonding lead 3 e inthe lower tier is 1st bond and each first bonding pad 4 c in the uppertier is 2nd bond. In the reverse bonding method in this embodiment, thefollowing measure is taken as illustrated in the sketch of “AFTER WIRECUT” in FIG. 25: a first bump electrode 2 g is formed beforehand on abonding pad to be the 2nd bond. (In this example, this bonding pad isone of the first bonding pads 4 c of the first semiconductor chip 4.) Atthis time, the following inclined plane 2 h is formed in the frontsurface of the first bump electrode 2 g by pressing the apical surface21 a of the capillary 21 against the front surface of the first bumpelectrode 2 g as illustrated in FIG. 25: the inclined plane 2 h whoseheight is reduced from the central part in the first front surface 4 aof the first semiconductor chip 4 toward the first chip side 4 d.

More detailed description will be given. As illustrated in the sketch of“AT TIME OF BUMP LANDING” in FIG. 25, the following processing iscarried out under the guidance of the capillary 21: the central part 2 dof the ball portion 2 c of the first wire 2 a is aligned with thecentral part 4 e of the first bonding pad 4 c (2nd side) and they arejoined together. At this time, heat and an ultrasonic wave are used tojoin the ball portion 2 c to the bonding pad 4 c. Thereafter, thecapillary 21 is moved up as illustrated in the sketch of “AT TIME OFBUMP FORMATION” in FIG. 25 and is slightly moved toward the firstbonding lead 3 e (1st bond) illustrated in FIG. 24. Further, asillustrated in the sketch of “AFTER BUMP COMPLETION,” the capillary 21is moved down and the ball portion 2 c is pressed and crushed by theinclined portion 21 b of the apical surface 21 a of the capillary 21.Thereafter, the first wire 2 a is cut and as a result, the first bumpelectrode 2 g is formed as illustrated in the sketch of “AFTER WIRECURE” in FIG. 25. At this time, the following inclined plane 2 h isformed in the front surface of the first bump electrode 2 g: theinclined plane 2 h whose height is reduced from the central part in thefirst front surface 4 a of the first semiconductor chip 4 toward thefirst chip side 4 d.

As illustrated in FIG. 26, subsequently, 1st bond joining in the reversebonding method is carried out on the first bonding lead 3 e of thewiring board 3. First, using the capillary 21, the ball portion 2 c ofthe first wire 2 a is joined to one of the multiple first bonding leads3 e of the wiring board 3. At this time, the first wire 2 a is arrangedabove the first bonding lead 3 e under the guidance of the capillary 21as illustrated in the sketch of “BEFORE 1ST SIDE JOINING” in FIG. 26.

Thereafter, the following processing is carried out as illustrated inthe sketch of “AT TIME OF 1ST SIDE BUMP LANDING” in FIG. 26: the ballportion 2 c is landed on the first bonding lead 3 e under the guidanceof the capillary 21 and then the ball portion 2 c is pressed against andjoined to the first bonding lead 3 e by the capillary 21. At this time,heat and an ultrasonic wave are used to join the ball portion 2 c to thebonding pad 4 c.

Thereafter, the capillary 21 is moved up as illustrated in the sketch of“AFTER 1ST SIDE JOINING” in FIG. 26.

As illustrated in FIG. 27, subsequently, 2nd bond is carried out. Inthis example, part of the first wire 2 a is joined to the front surfaceof the first bump electrode 2 g. First, it is set above the firstbonding pad 4 c of the first semiconductor chip 4 as illustrated in thesketch of “BEFORE 2ND SIDE JOINING” in FIG. 27. Then, as illustrated inthe sketches of “AT TIME OF WIRE LANDING” and “AT TIME OF JOININGCOMPLETION” in FIG. 27, the first wire 2 a is landed on the frontsurface of the first bump electrode 2 g formed beforehand under theguidance of the capillary 21. At this time, the inclined plane 2 h ofthe first bump electrode 2 g is pressed by the inclined portion 21 b ofthe apical surface 21 a of the capillary 21 in the following state: astate in which the central part 21 c of the capillary 21 is shifted fromthe central part 2 i of the first bump electrode 2 g in such a directionthat it goes away from the first chip side 4 d (inward). That is, theentire inclined plane 2 h of the first bump electrode 2 g is pressed bythe apical surface 21 a of the capillary 21.

As a result, bonding is carried out with both the thin portion 2 q andthe thick portion 2 r in the inclined plane 2 h of the first bumpelectrode 2 g crushed. This makes it possible to increase the joiningarea to enhance the joining strength.

Thereafter, as illustrated in the sketch of “AFTER WIRE CUT” in FIG. 27,the first wire 2 a is cut and the bonding of the first wire 2 a on the2nd side is completed. Over the first bonding pad 4 c, an end (part) 2 pof the first wire 2 a is joined to the inclined plane 2 h of the firstbump electrode 2 g.

Using the same reverse bonding method, the other first bonding leads 3 eof the wiring board 3 and the other first bonding pads 4 c of the firstsemiconductor chip 4 are electrically coupled with each other throughfirst wires 2 a.

Subsequently, the first bonding pads 4 c of the first semiconductor chip4 in the first tier and the second bonding pads 5 c of the secondsemiconductor chip 5 in the second tier are coupled with each other bythe reverse bonding method. In this example, the multiple first bondingpads 4 c and the multiple second bonding pads 5 c are respectivelyelectrically coupled with each other through multiple second wires 2 b.

First, a second bump electrode 2 m (Refer to FIG. 30) is formed over asecond bonding pad 5 c of the second semiconductor chip 5 to be the 2ndside by the same formation method as that for the first bump electrode 2g illustrated in FIG. 25. Also at the second bump electrode 2 m, at thistime, the inclined plane 2 s whose height is reduced toward the firstbonding pad 4 c in the lower tier is formed in the front surfacesimilarly with the inclined plane 2 h of the first bump electrode 2 g.

Thereafter, the following processing is carried out as illustrated inthe sketch of “BEFORE SECOND WIRE JOINING” in FIG. 28: the ball portion2 e of the second wire 2 b is arranged above the end 2 p of the firstwire 2 a joined to the first bump electrode 2 g over the first bondingpad 4 c of the first semiconductor chip 4 under the guidance of thecapillary 21. At this time the end 2 p of the first wire 2 a includesthe following portions as illustrated in FIG. 29: a first portion (thinwire area) 2 j; and a second portion (thick wire area) 2 k positionedcloser to the first chip side 4 d than the first portion 2 j is andlarger in thickness (thicker) than the first portion 2 j.

Thereafter, the following processing is carried out as illustrated inthe sketch of “AT TIME OF SECOND WIRE LANDING” in FIG. 28 and FIG. 29:the capillary 21 is moved down and the ball portion 2 e of the secondwire 2 b is pressed against and joined to the end 2 p of the first wire2 a and the first bump electrode 2 g by the capillary 21. In thisexample, the second wire 2 b is guided by the capillary 21 so that theball portion 2 e of the second wire 2 b is brought into contact with thefirst portion 2 j and second portion 2 k of the first wire 2 aillustrated in FIG. 29. Then the ball portion 2 e of the second wire 2 bis joined to the end 2 p of the first wire 2 a and the first bumpelectrode 2 g.

As a result, bonding is carried out with both the first portion 2 j andthe second portion 2 k at the end 2 p of the first wire 2 a crushed.This makes it possible to increase the joining area to enhance thejoining strength.

To enhance the joining strength between the first bump electrode 2 g andthe ball portion 2 e of the second wire 2 b, it is important to take themeasure illustrated in FIG. 29. That is, the first bump electrode 2 g,first wire 2 a, and second wire 2 b are bonded so that they do notprotrude beyond the pad width D of the first bonding pad 4 c of thefirst semiconductor chip 4. That is, to enhance the joining strength, itis important to join the ball portion 2 e of the second wire 2 b fromdirectly above the first bump electrode 2 g.

Preferably, the joining area between the second wire 2 b and the firstbump electrode 2 g is increased to enhance the joining strength bytaking the following measure: the ball portion 2 e of the second wire 2b is joined to the end 2 p of the first wire 2 a and the first bumpelectrode 2 g so that the following is implemented: the central part 2 fof the ball portion 2 e of the second wire 2 b overlaps with the centralpart 2 i of the first bump electrode 2 g.

Thereafter, as illustrated in the sketch of “AT TIME OF JOININGCOMPLETION” in FIG. 28, the capillary 21 is moved up and the wirebonding of the second wire 2 b on the 1st side is completed.

Subsequently, wire bonding of the second wire 2 b on the 2nd side iscarried out. (This is wire bonding to the second bonding pads 5 c of thesecond semiconductor chip 5 in the second tier.) In the assembly in thefirst embodiment, at this time, the path 21 e of the capillary 21illustrated in FIG. 30 to FIG. 32 is used to carry out wire bonding ofthe second wire 2 b on the 2nd side.

As illustrated in FIG. 30 to FIG. 32, first, the ball portion 2 e of thesecond wire 2 b is joined to the first bump electrode 2 g (refer to FIG.29) over the first bonding pad 4 c under the guidance of the capillary21. When the capillary 21 is subsequently moved from the first bondingpad 4 c to the second bonding pad 5 c, the following processing iscarried out: on the way, it is moved back toward the first bonding pad 4c along the second direction 21 d connecting the first bonding pad 4 cand the second bonding pad 5 c. That is, the capillary 21 is pulled upabove the first bonding pad 4 c and the pulled-up capillary 21 is movedin such a direction that it goes away from the second bonding pad 5 c asviewed in a plane. (This direction is the direction from directly abovethe first bonding pad 4 c toward the first chip side 4 d.) Subsequently,the capillary is cut back toward the second bonding pad 5 c in acontinuous action to form a curved point 2 n in the second wire 2 b.More specific description will be given. The capillary 21 is moved insuch a direction that it goes close to the second bonding pad 5 c asviewed in a plane. The capillary 21 is arranged closer to the secondbonding pad 5 c than when it is positioned directly above the firstbonding pad 4 c. Then the capillary 21 is moved again in such adirection that it goes away from the second bonding pad 5 c as viewed ina plane. (This direction is the direction from directly above the firstbonding pad 4 c toward the first chip side 4 d.) Then part of the secondwire 2 b is joined to the front surface of the second bump electrode 2 mformed over the second bonding pad 5 c.

More detailed description will be given. After joining on the 1st sideis completed as illustrated in FIG. 30, the capillary 21 is pulled upabove the first bonding pad 4 c. The second wire 2 b is thereby pulledout once in such a direction that it goes away from the second bondingpad 5 c. The capillary is further moved up and then moved toward thesecond bonding pad 5. Further, on the way from the first bonding pad 4 ctoward the second bonding pad 5 c, the capillary 21 is moved up.Thereafter, it is moved back toward the first bonding pad 4 c along thesecond direction 21 d illustrated in FIG. 32 and then cut back towardthe second bonding pad 5 c (X site in FIG. 30) in a continuous action.The curved point 2 n illustrated in FIG. 31 is thereby formed in thesecond wire 2 b. Thereafter, part of the second wire 2 b is joined tothe front surface of the second bump electrode 2 m formed over thesecond bonding pad 5 c.

When part of the second wire 2 b is joined to the second bump electrode2 m, the method of joining the first wire 2 a to the first bumpelectrode 2 g illustrated in FIG. 27 is used.

In the second bump electrode 2 m, there is formed the inclined plane 2s. Therefore, when part of the second wire is joined to the second bumpelectrode 2 m, force P is applied to the second wire 2 b. This force Pis produced by the inclined plane 2 s and the action of pressing forcefrom the apical surface 21 a of the capillary 21 as illustrated in FIG.31 and acts to push the second wire 2 b toward the first bonding pad 4 csubstantially horizontally. (This force P similarly acts at the inclinedplane 2 h of the first bump electrode 2 g as well.)

As the result of the application of this force P, the second wire 2 b issubstantially horizontally pushed out and thus the wire loop height canbe reduced over the second bonding pad 5 c (2nd side). This loop heightreduction is intended to implement the following: the height of the wire2 is reduced within the range where the semiconductor chip in the fourthtier and a semiconductor chip arranged planarly in the same positionthereabove overlap with each other as shown in S site in FIG. 35. Ifusual reverse bonding is carried out at S site, the wire 2 can bebrought into contact with the upper semiconductor chip. When theinclined plane 2 h is formed in the first bump electrode 2 g as in thefirst embodiment, the loop height of the wire 2 can be reduced at S siteto prevent this.

FIG. 67 illustrates a comparative example of the inclined plane 2 s ofthe second bump electrode 2 m investigated by the present inventors. Inthis comparative example, the inclination direction in which the heightof the inclined plane 2 s (same with the inclined plane 2 h of the firstbump electrode 2 g) is reduced is reversed relative to the first bondingpad 4 c. That is, the inclined plane 2 s has an inclination whose heightis increased toward the first bonding pad 4 c.

In the sketches of “BEFORE PRESSING” and “AFTER PRESSING” in FIG. 67,the inclined plane 2 s of the second bump electrode 2 m is so inclinedthat it becomes higher toward the first bonding pad 4 c (refer to FIG.31) in wire bonding on the 2nd side. In this case, the following takesplace during wire bonding as illustrated in the sketches: the secondwire 2 b is joined so that it is inclined in such a direction that itbecomes higher toward the first bonding pad 4 c (direction Y in which itis lifted). As a result, the wire loop height cannot be reduced over thesecond bonding pad 5 c (2nd side).

Therefore, it is desirable that the inclined plane 2 s of the secondbump electrode 2 m should be so inclined that it becomes lower towardthe first bonding pad 4 c in the lower tiers. (This is the same with theinclined plane 2 h of the first bump electrode 2 g.)

In wire bonding on the 2nd side, as illustrated in FIG. 31, the secondwire 2 b is pushed out toward the first bonding pad 4 c by force Parising from the following: the inclined plane 2 s inclined toward thefirst bonding pad 4 c in the lower tier formed over the second bumpelectrode 2 m and the action of pressing force from the apical surface21 a of the capillary 21. However, the curved point 2 n is formed in thesecond wire 2 b and it is high in rigidity in proximity to the curvedpoint 2 n. Therefore, the second wire 2 b does not laterally topple andis straightly pushed out in the area (Q site) located above the firstbonding pad 4 c as illustrated in FIG. 32.

FIG. 68 to FIG. 70 illustrate the path 21 e of a capillary 21 in acomparative example investigated by the present inventors. According tothis path 21 e, the processing is carried out as follows: after wirebonding on the 1st side is completed at the first bonding pad 4 c, thecapillary 21 is moved up to once pull up the second wire 2 b in such adirection that it goes away from the second bonding pad 5 c; and thecapillary is further moved up and then moved toward the second bondingpad 5 and wire bonding on the 2nd side at the second bonding pad 5 c isdirectly started. That is, the above path does not involve the followingoperation unlike the path 21 e of the capillary 21 in the firstembodiment illustrated in FIG. 30: the capillary is moved back towardthe first bonding pad 4 c once and then cut back toward the secondbonding pad 5 c in a continuous action.

Therefore, such a curved point 2 n as illustrated in FIG. 31 is notformed in the second wire 2 b. Therefore, a problem arises when thesecond wire 2 b is pushed out toward the first bonding pad 4 c by forceP arising from the following as illustrated in FIG. 69: the inclinedplane 2 s formed in the second bump electrode 2 m and the action ofpressing force from the apical surface 21 a of the capillary 21. Asillustrated in R site in FIG. 70, a side toppling phenomenon occurs inthe second wire 2 b in proximity to above the first bonding pad 4 c.This causes bonding failure, such as contact with an adjacent secondwire 2 b.

When the path 21 e of the capillary 21 in the first embodimentillustrated in FIG. 30 is adopted, the curved point 2 n is formed in thesecond wire 2 b and thus the side toppling phenomenon can be prevented.Further, the loop height of a wire formed by the wire bonding step canbe reduced as illustrated in FIG. 24. For this reason, the followingproblem can be suppressed even when another semiconductor chip isarranged directly above at steps (die bonding steps) of placing thesemiconductor chips in the fifth and following tiers: a problem ofcontact between a wire and a semiconductor chip arranged directly above.In this embodiment, the wire bonding method illustrated in FIG. 30 isnot adopted at the wire bonding step for electrically coupling thesemiconductor chip in the first tier to the wiring board 3 for the sakeof simplification of the process. As illustrated in FIG. 4, this isbecause the distance between the semiconductor chip in the first tierand the semiconductor chip arranged directly above this semiconductorchip is larger than the following distance: the distance between each ofthe semiconductor chips in the second to fourth tiers (especially, inthe fourth tier) and the semiconductor chip arranged directlythereabove. However, the wire bonding method illustrated in FIG. 30 mayalso be applied to the semiconductor chip in the first tier, needless toadd.

As mentioned above, highly reliable wire bonding with a reduced loopheight can be achieved by taking the following measure: the second bumpelectrode 2 m in the first embodiment is provided with the inclinedplane 2 s (same with the inclined plane 2 h of the first bump electrode2 g); and the path 21 e of the capillary 21 illustrated in FIG. 30 isused to carry out wire bonding.

Wire bonding for the third tier and the fourth tier is carried outsimilarly with the wire bonding (reverse bonding) for coupling the firstsemiconductor chip 4 in the first tier and the second semiconductor chip5 in the second tier through second wires 2 b. This completes wirebonding for up to the fourth tier.

<<Die Bonding Step for Fifth Tier to Eighth Tier>>

As illustrated in FIG. 33 and FIG. 34, subsequently, die bonding for thefifth tier to the eighth tier is carried out. In die bonding for thefifth tier to the eighth tier, the lamination direction is changed by180 degrees from that in die bonding for the first tier to the fourthtier and the lamination direction is turned back at the fifth tier.However, this die bonding is identical with that for the first tier andthe fourth tier in that semiconductor chips are shifted at every tierand laminated stepwise. At this time, the semiconductor chips arelaminated so that the bonding pads in each tier are arranged on theopposite side to those in the first tier to the fourth tier.

In the fifth tier as the first tier in turn-back lamination, asillustrated in FIG. 33, a third semiconductor chip 6 identical inthickness with the first semiconductor chip 4 and thicker than thesecond semiconductor chip 5 is placed. As illustrated in FIG. 35, thethird semiconductor chip 6 includes: a third front surface 6 aquadrilateral in planar shape; multiple third bonding pads (electrodepads, pads to which a wire 2 is directly bonded) 6 c formed along (only)the third chip side 6 d of the third front surface 6 a; and a third backsurface 6 b opposite to the third front surface 6 a. Further, a firstadhesive layer 8 as a first adhesive layer large in thickness is stuckto the third back surface 6 b of the third semiconductor chip 6.Therefore, the third semiconductor chip 6 is placed through the firstadhesive layer 8. The third semiconductor chip 6 is a memory chip havingthe same functions as the first semiconductor chip 4.

The thickness of the third semiconductor chip 6 is within a range of0.040 to 0.200 mm, and 0.055 mm in this embodiment. The thickness of thefirst adhesive layer 8 stuck to the third semiconductor chip 6 is withina range of 0.010 to 0.050 mm, and 0.020 mm in this embodiment. In thiscase, the total thickness of the third semiconductor chip 6 and thefirst adhesive layer 8 is 0.075 mm.

In die bonding of the third semiconductor chip 6 in the fifth tier, itis placed (arranged, laminated) over the second semiconductor chip 5 inthe fourth tier so that the following is implemented: as illustrated inFIG. 35, the distance between the third chip side 6 d and the secondboard side 3 m is shorter than the following distance as viewed in aplane and the multiple second bonding pads 5 c are exposed from thethird semiconductor chip 6: the distance between the third chip side 6 d(or the chip side (the other short side) opposed to the third chip side6 d) and the first board side 3 k. In other words, the thirdsemiconductor chip 6 in the fifth tier is placed so that the third chipside 6 d is arranged closer to the second board side 3 m than to thefirst board side 3 k. That is, the semiconductor chip 6 in the fifthtier is laminated (placed) stepwise with its lamination directionchanged by 180 degrees from those of the semiconductor chips 4, 5 in thefirst to fourth tiers so that the following is implemented: the thirdchip side (side on which the bonding pads 6 c are arranged) 6 d of thethird semiconductor chip 6 faces toward the other side (second boardside) 3 m of the two short sides of the wiring board 3; and thesemiconductor chip 6 is positioned in the device area (the upper surface3 a of the wiring board 3) as viewed in a plane.

When the thickness (Tw1) of the third semiconductor chip 6 in the fifthtier and the thickness (Td1) of the first adhesive layer 8 are addedtogether, the total thickness of Tw1+Td1 is obtained. Because of therelation with the wire loop height (Hw) in FIG. 35, it is required toprevent interference between the wire 2 in the lower tier (fourth tier)and the fourth semiconductor chip 7 in the upper tier (sixth tier). Toachieve this, it is required to meet the requirement for the clearance(D)=(Tw1+Td1)−Hw>0 as illustrated in FIG. 33.

As mentioned above, the third semiconductor chip 6 is identical inthickness with the first semiconductor chip 4 and thicker than thesecond semiconductor chip 5. Further, the first adhesive layer 8 isthick; therefore, the following can be implemented by adding thethickness of the third semiconductor chip 6 and the thickness of thefirst adhesive layer 8: it is possible to ensure a height sufficient toprevent interference between the loop of the wire 2 in the directlylower tier (fourth tier) and the fourth semiconductor chip 7 locateddirectly above (sixth tier) as shown in S site in FIG. 35; and it ispossible to prevent (reduce) interference (contact) between the wire 2in the lower tier (fourth tier) and the fourth semiconductor chip 7located directly above.

In wire bonding to the second bonding pads 5 c of the secondsemiconductor chip 5 in the fourth tier, the following can beimplemented. The second wire 2 b whose loop height is reduced by theinclined plane 2 s of the second bump electrode 2 m as illustrated inFIG. 31. Therefore, a sufficient clearance can be ensured at S site inFIG. 35 by a combination of the low loop height and the large totalthickness of the third semiconductor chip 6 and the first adhesive layer8 that are both thick. Thus it is possible to prevent (reduce)interference between the wire 2 in the lower tier (fourth tier) and thefourth semiconductor chip 7 located directly above.

In the first tier in the turn-back lamination, a portion of the chip endis overhanged (protruded) from the chip in the lower tier. In theoverhanged portion, there are bonding pads whose lower parts are notsupported by anything and they must withstand bonding force during wirebonding. Therefore, use of the thick-type third semiconductor chip 6makes it possible to enhance the strength of the chip itself and prevent(reduce) chip breakage due to bonding force during wire bonding.

Since there are portions whose lower parts are not supported by anythingin the overhanged area at the chip end, chip fracture is prone to becaused by pressure from a resin flow during resin molding. Therefore,use of the thick-type third semiconductor chip 6 makes it possible toenhance the strength of the chip itself similarly with the foregoing. Inaddition, it makes it possible to prevent (reduce) the occurrence ofchip fracture due to pressure from a resin flow during resin molding.

As illustrated in FIG. 34, subsequently, the second and following tiers(the sixth tier to the eighth tier) after turn-back are laminated. Thatis, die bonding is carried out for the sixth tier to the eighth tier. Atthis time, fourth semiconductor chips 7 as thin-type semiconductor chipslike the second semiconductor chips 5 in the second tier to the fourthtier are used.

The fourth semiconductor chip 7 includes: a fourth front surface 7 aquadrilateral in planar shape; multiple fourth bonding pads (electrodepads, pads to which a wire 2 is directly bonded) 7 c formed along (only)the fourth chip side 7 d of the fourth front surface 7 a; and a fourthback surface 7 b opposite to the fourth front surface 7 a. Further, asecond adhesive layer 9 as a second adhesive layer small in thickness isstuck to the fourth back surface 7 b of the fourth semiconductor chip 7.Therefore, the fourth semiconductor chip 7 is placed through the secondadhesive layer 9. The fourth semiconductor chip 7 is a memory chiphaving the same functions as the second semiconductor chip 5.

The thickness (Tw2) of the fourth semiconductor chip 7 is within a rangeof 0.010 to 0.030 mm similarly with the second semiconductor chip 5 andis, for example, 0.020 mm. The thickness (Td2) of the second adhesivelayer 9 stuck to the fourth semiconductor chip 7 is within a range of0.003 to 0.010 mm and is, for example, 0.005 mm. In this case, the totalthickness of the fourth semiconductor chip 7 and the second adhesivelayer 9 is 0.025 mm.

In die bonding of the fourth semiconductor chip 7 in the sixth tier, itis placed (arranged, laminated) over the third semiconductor chip 6 inthe fifth tier so that the following is implemented: as illustrated inFIG. 35, the distance between the fourth chip side 7 d and the secondboard side 3 m is shorter than the following distance as viewed in aplane and the multiple third bonding pads 6 c are exposed form thefourth semiconductor chip 7: the distance between the fourth chip side 7d (or the chip side (the other short side) opposed to the fourth chipside 7 d) and the first board side 3 k. In other words, the fourthsemiconductor chip 7 in the sixth tier is placed so that the fourth chipside 7 d is arranged closer to the second board side 3 m than to thefirst board side 3 k. That is, the fourth semiconductor chip 7 in thesixth tier is laminated (placed) stepwise with its lamination directionmatched with the semiconductor chip 6 in the fifth tier so that thefollowing is implemented: the fourth chip side (side on which thebonding pads 7 c are arranged) 7 d of the fourth semiconductor chip 7faces toward the other side (second board side) 3 m of the two shortsides of the wiring board 3; and the semiconductor chip 7 is positionedin the device area (the upper surface 3 a of the wiring board 3) asviewed in a plane.

Also in die bonding for the seventh tier and the eighth tier, the samesemiconductor chip as the fourth semiconductor chip 7 is used and thisdie bonding is carried out as for the sixth tier.

As mentioned above, a combination of the fourth semiconductor chip 7 andthe second adhesive layer 9 that are both thin is used in die bondingfor the sixth tier to the eighth tier. This makes it possible to reducethe overall thickness of the 16-tiered laminate to reduce the thicknessof the LGA 1.

In each of the semiconductor chips in the fifth tier to the eighth tier,the bonding pads in each tier are arranged on the second bonding lead 3f side of the wiring board 3.

This completes die bonding for the fifth tier to the eighth tier. In thefirst tier to the eighth tier, semiconductor chips are used as follows:the thick-type first semiconductor chip 4 and third semiconductor chip 6are respectively used in the first tier and the fifth tier; and thethin-type second semiconductor chip 5 and fourth semiconductor chip 7are respectively used in the second tier to the fourth tier and in thesixth tier to the eighth tier. The first semiconductor chip 4 and thethird semiconductor chip 6 are both thicker than the secondsemiconductor chip 5 and the fourth semiconductor chip 7. That is, thethickness of the LGA 1 can be reduced by using as many thin-typesemiconductor chips as possible.

<<Wire Bonding Step for Fifth Tier to Eighth Tier>>

As illustrated in FIG. 35, subsequently, wire bonding (reverse bonding)is carried out for the fifth tier to the eighth tier. The wire bondingfor the fifth tier to the eighth tier is different from the wire bondingfor the first tier to the fourth tier only in that the direction ofwiring in each tier is changed by 180°. In the other respects, the wirebonding for the fifth tier to the eighth tier is exactly the same asthat for the first tier to the fourth tier.

First, wire bonding is carried out for the third semiconductor chip 6 inthe fifth tier. That is, the multiple second bonding leads 3 f of thewiring board 3 and the multiple third bonding pads 6 c of the thirdsemiconductor chip 6 are respectively electrically coupled togetherthrough multiple third wires 2 t by the reverse bonding method.

At this time, a first bump electrode 2 g is formed beforehand on a thirdbonding pad 6 c of the third semiconductor chip 6 equivalent to the 2ndside as in wire bonding for the first semiconductor chip 4 in the firsttier. However, the inclined plane 2 h formed in the first bump electrode2 g over the third bonding pad 6 c is inclined so that it becomes lowertoward the second bonding leads 3 f located in the lower tier.

Reverse bonding in the third semiconductor chip 6 in the fifth tier isthe same as reverse bonding in the first semiconductor chip 4. First, athird wire 2 t is joined to a second bonding lead 3 f of the wiringboard 3 as the 1st side; thereafter, part of the third wire 2 t iselectrically coupled to the first bump electrode 2 g over the thirdbonding pad 6 c of the third semiconductor chip 6 as the 2nd side. Thiscompletes the reverse bonding in the third semiconductor chip 6 in thefifth tier.

Thereafter, wire bonding is carried out for the sixth tier to the eighthtier. The wire bonding for the sixth tier to the eighth tier is exactlythe same as the wire bonding for the second tier to the fourth tierexcept the direction of wiring. More specific description will be given.A second bump electrode 2 m having an inclined plane 2 s is formedbeforehand on a bonding pad of a semiconductor chip in the upper tier(2nd side). In this state, wire bonding on the 1st side is carried outon a bonding pad of a semiconductor chip in the lower tier; thereafter,wire bonding on the 2nd side is carried out on the inclined plane 2 s ofthe second bump electrode 2 m over the bonding pad of the semiconductorchip in the upper tier.

In wire bonding in the fourth semiconductor chip 7 in the sixth tier,for example, the following processing is carried out: the multiple thirdbonding pads 6 c of the third semiconductor chip 6 in the fifth tier andthe multiple fourth bonding pads 7 c of the fourth semiconductor chip 7in the sixth tier are respectively electrically coupled together throughmultiple fourth wires 2 u by reverse bonding.

At this time, a second bump electrode 2 m is formed beforehand in afourth bonding pad 7 c of the fourth semiconductor chip 7 equivalent tothe 2nd side as in wire bonding in the second semiconductor chip 5 inthe second tier. However, the inclined plane 2 s formed in the secondbump electrode 2 m over the fourth bonding pad 7 c is inclined so thatit becomes lower toward the third bonding pads 6 c located in the lowertier.

Reverse bonding in the fourth semiconductor chip 7 in the sixth tier isthe same as reverse bonding in the second semiconductor chip 5. First, afourth wire 2 u is joined as the 1st side to part of the third wire 2 tover the third bonding pad 6 c of the third semiconductor chip 6;thereafter, part of the fourth wire 2 u is electrically coupled to thesecond bump electrode 2 m over the fourth bonding pad 7 c of the fourthsemiconductor chip 7 as the 2nd side. This completes the reverse bondingin the fourth semiconductor chip 7 in the sixth tier.

The wire bonding method for the seventh tier and the eighth tier is thesame as the reverse bonding method for the fourth semiconductor chip 7in the sixth tier.

The wire bonding for the fifth tier to the eighth tier is carried out asmentioned above. This makes it possible to achieve highly reliable wirebonding with a reduced loop height as in the wire bonding for the firsttier to the fourth tier.

As mentioned above, the following takes place in the main surface (backsurface, lower surface) 6 b of the semiconductor chip 6 in the fifthtier: the area that planarly overlaps with the bonding pads 6 c of thesemiconductor chip 6 is not supported by the semiconductor chip (thesemiconductor chip in the fourth tier in this case) positioned in thelower tier. That is, the bonding pads 6 c of the semiconductor chip 6are formed in a so-called overhang area. For this reason, when thecapillary 21 used at the wire bonding step is pressed against such abonding pad 6 c, chip cracking is prone to occur. In this embodiment,however, the semiconductor chip 4 having the first thickness (Tw1)illustrated in FIG. 5 is used as the semiconductor chip in the fifthtier. For this reason, the semiconductor chip is less prone to bend andeven though force from the capillary 21 is applied to the overhang area,the occurrence of chip cracking can be suppressed.

As mentioned above, further, the following semiconductor chip is used asthe semiconductor chip placed in the fifth tier: the semiconductor chip4 having the first thickness (Tw1) larger than the second thickness(Tw2) of the semiconductor chip 5 used in the second to fourth tiers (orthe sixth to eighth tiers). As illustrated in FIG. 4, this makes itpossible to increase the distance between the semiconductor chip in thefourth tier and the semiconductor chip in the sixth tier positionedabove this semiconductor chip. In this embodiment, in addition, thefollowing adhesive layer is used as the adhesive layer used to place thesemiconductor chip in the fifth tier: the adhesive layer 8 having thefirst thickness (Td1) larger than the second thickness (Td2) of theadhesive layer 9 used in the second to fourth tiers (or the sixth toeighth tiers). For this reason, it is possible to further increase thedistance between the semiconductor chip in the fourth tier and thesemiconductor chip in the sixth tier positioned above this semiconductorchip. This makes it possible to prevent a problem of contact between awire bonded to a bonding pad of the semiconductor chip in the fourthtier and the semiconductor chip in the sixth tier positioned directlyabove this semiconductor chip. In this embodiment, further, such a wirebonding method as illustrated in FIG. 30 is adopted at the wire bondingstep for the semiconductor chip in the fourth tier. Since the loopheight of a formed wire can be further reduced, therefore, it ispossible to more reliably prevent a problem of contact between a wireand the semiconductor chip in the upper tier.

<<Die Bonding Step for Ninth Tier to 12th Tier>>

As illustrated in FIG. 36, subsequently, die bonding is carried out forthe ninth tier to the 12th tier. The die bonding for the ninth tier tothe 12th tier is exactly the same as the die bonding for the first tierto the fourth tier. The thick-type first semiconductor chip 4 is used inthe ninth tier and the thin-type second semiconductor chip 5 is used inthe 10th tier to the 12th tier.

Since the thick-type first semiconductor chip 4 is placed in the ninthtier at a turn-back of lamination, the following can be implemented: itis possible to ensure a height sufficient to prevent interferencebetween the loop of a wire 2 in the directly lower tier (eighth tier)and the second semiconductor chip 5 located directly above (10th tier);and it is possible to prevent (reduce) interference (contact) betweenthe wire 2 in the lower tier (eighth tier) and the second semiconductorchip 5 located directly above.

In the first tier in the turn-back lamination (the ninth tier), aportion of the chip end is overhanged (protruded) from the chip in thelower tier. In the overhanged portion, there are bonding pads whoselower parts are not supported by anything and they must withstandbonding force during wire bonding. Therefore, use of the thick-typefirst semiconductor chip 4 makes it possible to enhance the strength ofthe chip itself and prevent (reduce) chip breakage due to bonding forceduring wire bonding.

Since there are portions whose lower parts are not supported by anythingin the overhanged area at the chip end, chip fracture is prone to becaused by pressure from a resin flow during resin molding. Therefore,use of the thick-type first semiconductor chip 4 makes it possible toenhance the strength of the chip itself similarly with the foregoing. Inaddition, it makes it possible to prevent (reduce) the occurrence ofchip fracture due to pressure from a resin flow during resin molding.

As mentioned above, a combination of the second semiconductor chip 5 andthe second adhesive layer 9 that are both thin is used in die bondingfor the 10th tier to the 12th tier. This makes it possible to reduce theoverall thickness of the 16-tiered laminate to reduce the thickness ofthe LGA 1.

<<Wire Bonding Step for Ninth Tier to 12th Tier>>

Subsequently, the wire bonding for the ninth tier to the 12th tier,illustrated in FIG. 36 is carried out. The wire bonding for the ninthtier to the 12th tier is exactly the same as the wire bonding (reversebonding) for the first tier to the fourth tier; therefore, thedescription thereof will be omitted. Also in the wire bonding for theninth tier to the 12th tier, highly reliable wire bonding with a reducedloop height can be achieved as in the wire bonding for the first tier tothe fourth tier.

<<Die Bonding Step for 13th Tier to 16th Tier>>

As illustrated in FIG. 37, subsequently, die bonding is carried out forthe 13th tier. The die bonding for the 13th tier is exactly the same asthe die bonding for the fifth tier as the first tier after a turn-backof lamination. That is, a combination of the third semiconductor chip 6and the first adhesive layer 8 that are both thick is used.

This makes it possible to ensure a height sufficient to preventinterference between the loop of a wire 2 in the directly lower tier(12th tier) and the fourth semiconductor chip 7 lactated directly above(14th tier). Therefore, it is possible to prevent (reduce) interference(contact) between the wire 2 in the lower tier (12th tier) and thefourth semiconductor chip 7 located directly above.

In the first tier in the turn-back lamination (13th tier), a portion ofthe chip end is overhanged (protruded) from the chip in the lower tier.In the overhanged portion, there are bonding pads whose lower parts arenot supported by anything and they must withstand bonding force duringwire bonding. Therefore, use of the thick-type third semiconductor chip6 makes it possible to enhance the strength of the chip itself andprevent (reduce) chip breakage due to bonding force during wire bonding.

Since there are portions whose lower parts are not supported by anythingin the overhanged area at the chip end, chip fracture is prone to becaused by pressure from a resin flow during resin molding. Therefore,use of the thick-type third semiconductor chip 6 makes it possible toenhance the strength of the chip itself similarly with the foregoing. Inaddition, it makes it possible to prevent (reduce) the occurrence ofchip fracture due to pressure from a resin flow during resin molding.

Subsequently, the die bonding for the 14th tier to the 16th tier (theuppermost tier) illustrated in FIG. 38 is carried out. The die bondingfor the 14th tier and the 15th tier is the same as the die bonding forthe sixth tier and the seventh tier. A combination of the thin-typefourth semiconductor chip 7 and the thin second adhesive layer 9 isused.

This makes it possible to reduce the overall thickness of the 16-tieredlaminate to reduce the thickness of the LGA 1.

In the 16th tier, which is the uppermost tier, a combination of thefirst semiconductor chip 4 and the first adhesive layer 8 that are boththick is used.

The semiconductor chip in the 16th tier as the uppermost tier is notespecially supported by any member on its upper surface side (firstfront surface 4 a side). Therefore, the foregoing is a measure againstchip fracture prone to be caused by pressure from a resin flow duringresin molding. Use of the thick-type first semiconductor chip 4 also inthe 16th tier makes it possible to implement the following: the strengthof the chip itself is enhanced and the occurrence of chip fracture, chipbending, and chip peeling-off due to pressure from a resin flow duringresin molding is prevented (reduced).

<<Wire Bonding Step for 13th Tier to 16th Tier>>

Subsequently, the wire bonding for the 13th tier to the 16th tier,illustrated in FIG. 39 is carried out. The wire bonding for the 13thtier to the 16th tier is exactly the same as the wire bonding (reversebonding) for the fifth tier to the eighth tier; therefore, thedescription thereof will be omitted. Also in the wire bonding for the13th tier to the 16th tier, highly reliable wire bonding with a reducedloop height can be achieved as in the wire bonding for the fifth tier tothe eighth tier.

<<Molding Step>>

Description will be given to a resin molding step and a segmentationstep carried out after the wire bonding step in the assembly of the LGA1. FIG. 40 is a plan view illustrating an example of a structureobtained after resin molding in the assembly of the semiconductor deviceillustrated in FIG. 1; FIG. 41 is a sectional view illustrating anexample of a structure obtained after the resin molding illustrated inFIG. 40; FIG. 42 is a plan view illustrating an example of a structureobtained at the time of segmentation in the assembly of thesemiconductor device illustrated in FIG. 1; and FIG. 43 is a sectionalview illustrating an example of the structure obtained at the time ofsegmentation illustrated in FIG. 42.

In the assembly of LGA 1, resin molding is carried out after thecompletion of the wire bonding step. At the resin molding step, asillustrated in FIG. 40 and FIG. 41, a blanket sealing body 22 is formedover the multiple substrate 20 that underwent wire bonding using sealingresin by, for example, transfer molding or the like.

Sealing resin containing filler is used as the sealing resin for formingthe blanket sealing body 22. As shown in T site in FIG. 39, it isdifficult to fill the following gap with sealing resin: the gap 23sandwiched between the overhanged portion of the second semiconductorchip 5 in the second tier and the wiring board 3 at the lateral of thefirst semiconductor chip 4 in the first tier. The height of this gap 23is determined by the thickness of the first semiconductor chip 4 plusthe thickness of the first adhesive layer 8. In case of the LGA 1 in thefirst embodiment, the thickness of the first semiconductor chip 4 is0.055 mm and the thickness of the first adhesive layer 8 is 0.020 mm.The sum of them is 0.075 mm (75 μm). In this case, as a result, theheight of the gap 23 is 0.075 mm (75 μm).

Therefore, the particle size of the filler contained in the sealingresin must be so small that it can enter this gap 23. For example, afiller that passes through a mesh of 50 μm (0.050 mm) is used. A sealingresin containing filler that can pass through a mesh of 50 μm can besufficiently filled in the gap 23 with a height of 75 μm.

In cases where the semiconductor device is of card type, it is requiredto ensure strength with the sealing body 10. The sealing body 10 formedof a sealing resin containing filler that can pass through a mesh of 50μm makes it possible to ensure strength.

In the front surface (or the back surface) of each semiconductor chip, aportion (so-called overhang area) that is not supported by any othersemiconductor chip is prone to be warped by resin filling pressure. Inthis embodiment, as illustrated in FIG. 4, the semiconductor chips inthe fifth, ninth, 13th, and 16th tiers have such an overhang area.

In this embodiment, however, the semiconductor chip 4 having the firstthickness (Tw1) illustrated in FIG. 5 is used as the semiconductor chipsin the fifth, ninth, 13th, and 16th tiers. In other words, asemiconductor chip whose thickness is larger than the thickness of eachof the semiconductor chips 5 in the second to fourth, sixth to eighth,10th to 12th, 14th, and 15th tiers. For this reason, even though resinfilling pressure produced at the molding step is applied to theseoverhang areas, chip cracking can be suppressed.

<<Segmentation Step>>

As illustrated in FIG. 42 and FIG. 43, subsequently, segmentation iscarried out to cut the workpiece along imaginary lines 24. When theworkpiece is cut, both the blanket sealing body 22 and the multiplesubstrate 20 are cut together by, for example, blade dicing.

This completes the assembly of the LGA 1 in the first embodimentillustrated in FIG. 1 and FIG. 2.

Modifications to First Embodiment

Description will be given to modifications to the first embodiment.

FIG. 44 is a perspective view illustrating the structure of asemiconductor device in a first modification to the first embodiment ofthe invention; FIG. 45 is a perspective view illustrating an example ofthe structure of the semiconductor device in FIG. 44 on the back surfaceside; and FIG. 46 is a sectional view illustrating the structure of asemiconductor device in a second modification to the first embodiment ofthe invention. FIG. 47 is a plan view illustrating the structure of asemiconductor device in a third modification to the first embodiment ofthe invention with a sealing body seen through; FIG. 48 is a sectionalview illustrating an example of a structure obtained by cutting thesemiconductor device along line A-A of FIG. 47; and FIG. 49 is asectional view illustrating an example of a structure obtained bycutting the semiconductor device along line B-B of FIG. 47.

The modification illustrated in FIG. 44 and FIG. 45 is a case where thesemiconductor device is a card-type semiconductor package 25. In thesemiconductor device, the structure, illustrated in FIG. 39, in whichmultiple thin-type semiconductor chips are laminated over a basematerial, is incorporated like the LGA 1 in the first embodiment. Thecard-type semiconductor package 25 is, for example, a microminiaturememory card or the like that can be loaded into a card slot of apersonal computer and is formed by laminating multiple flash memorychips (nonvolatile memories) over a base material.

The second modification illustrated in FIG. 46 is the structure of a16-tiered chip laminate in which semiconductor chips are laminated byeight tiers and only one 180-degree turn-back lamination is included onits way. Also in this case, a combination of the thick-type firstsemiconductor chip 4 (or third semiconductor chip 6) and the thick firstadhesive layer 8 is used in the following tiers: the first tier, theninth tier as the first tier after a turn-back lamination, and the 16thtier as the uppermost tier. As a result, the effect of ensuring thestrength of the chips themselves and ensuring the height of steps can beobtained as in the LGA 1 in the first embodiment.

A combination of the thin-type second semiconductor chip 5 (or fourthsemiconductor chip 7) and the thin second adhesive layer 9 is used inthe second tier to the eighth tier and in the 10th tier to the 15thtier. As a result, the effect of reduction in the thickness of thesemiconductor device can be obtained as in the LGA 1.

The third modification illustrated in FIG. 47 to FIG. 49 is thestructure of a 16-tiered chip laminate in which the lamination directionis changed by 90 degrees at every four tiers. Also in this case, acombination of the thick-type first semiconductor chip 4 (or thirdsemiconductor chip 6) and the thick first adhesive layer 8 is used inthe following tiers: the first tier; the fifth tier after the laminationdirection is changed by 90 degrees; the ninth tier after the laminationdirection is changed by 90 degrees again; the 13th tier after thelamination direction is changed by 90 degrees once again; and the 16thtier (the uppermost tier). As a result, the effect of ensuring thestrength of the chips themselves and ensuring the height of steps can beobtained as in the LGA 1 in the first embodiment.

A combination of the thin-type second semiconductor chip 5 (or fourthsemiconductor chip 7) and the thin second adhesive layer 9 is used inthe following tiers: the second tier to the fourth tier, the sixth tierto the eighth tier, the 10th tier to the 12th tier, the 14th tier, andthe 15th tier. As a result, the effect of reduction in the thickness ofthe semiconductor device can be obtained as in the LGA 1.

Since the lamination direction is changed three times by 90 degrees, itis possible to reduce the projected area of the laminate of thesemiconductor chips and reduce the thickness of the semiconductordevice.

Second Embodiment

FIG. 50 is a plan view illustrating an example of the structure of asemiconductor device in the second embodiment of the invention with asealing body seen through; FIG. 51 is a sectional view illustrating anexample of the structure obtained by cutting the semiconductor devicealong line A-A of FIG. 50; FIG. 52 is a sectional view illustrating anexample of the structure obtained by cutting the semiconductor devicealong line B-B of FIG. 50; and FIG. 53 is an enlarged partial sectionalview illustrating the structure of a semiconductor device in a firstmodification to the second embodiment of the invention.

The semiconductor device in the second embodiment illustrated in FIG. 50to FIG. 52 is obtained by laminating thin-type semiconductor chips in 16tiers over a wiring board 3 as the base material as in the firstembodiment. The semiconductor device has such a structure thatsemiconductor chips are laminated by eight tiers with the laminationdirection changed by 90 degrees only once on the way. A combination ofthe thick-type first semiconductor chip 4 (or third semiconductor chip6) and the thick first adhesive layer 8 is used only in the first tierand the 16th tier as the uppermost tier. A combination of the thin-typesecond semiconductor chip 5 (or fourth semiconductor chip 7) and thethin second adhesive layer 9 is used in the other intermediate tiers.

The lamination direction is changed only by 90 degrees. Therefore, evenat the place of lamination direction change, a wire 2 in the lower tieris not brought into contact with the semiconductor chip in the uppertier and it is unnecessary to ensure a chip height sufficient for a wireloop. Therefore, a combination of the thin-type second semiconductorchip 5 (or fourth semiconductor chip 7) and the thin second adhesivelayer 9 can be used in the tiers other than the first tier and the 16thtier as the uppermost tier. This makes it possible to reduce the heightof the chip laminate to reduce the thickness of the semiconductordevice.

However, a thick-type semiconductor chip may be used as thesemiconductor chip in the ninth tier as the first tier after laminationdirection change. This makes it possible to suppress the occurrence ofchip cracking due to the following force: force produced when a wire 2is joined to a bonding pad formed in a portion that is not supported bythe semiconductor chip in the eighth tier as at U site in FIG. 51.

Up to this point, concrete description has been given to the inventionmade by the present inventors based on embodiments of the invention.However, the invention is not limited to these embodiments and can bevariously modified without departing from its subject matter, needlessto add.

For example, the semiconductor device may be configured as in the firstmodification to fifth modification described below:

(First Modification)

FIG. 53 illustrates the first modification in which the thin-type secondsemiconductor chip 5 (or fourth semiconductor chip 7) acquired by thedicing method, illustrated in FIG. 12, described in relation to thefirst embodiment is used in all the 16 tiers and laminated. The firstmodification has a structure in which turn-back lamination is notcarried out. Also in this semiconductor device with such a laminatedstructure, chip cracking can be suppressed even when the thickness ofthe semiconductor wafer is reduced. This is done by advancing a bladetoward the reference portion formed in the semiconductor wafer, asmentioned above, at the dicing step for the semiconductor wafer.However, since semiconductor chips rectangular in planar shape areplaced stepwise in multiple tiers with an identical laminationdirection, the first modification is unsuitable for semiconductor devicesize reduction as compared with such a laminated structure as in thefirst embodiment.

The number of laminated thin-type second semiconductor chips 5 (orfourth semiconductor chips 7) is not limited to 16 and they may belaminated in any number of tiers as long as the number is two or above.

(Second Modification)

Description will be given to the second modification.

FIG. 54 is a perspective view illustrating an example of the structureof a semiconductor device in the second modification (one-side mounting)to the second embodiment of the invention with a sealing body seenthrough; FIG. 55 is a sectional view illustrating an example of a16-tiered chip laminated structure obtained by cutting the semiconductordevice along line A-A of FIG. 54; FIG. 56 is a sectional viewillustrating an example of the 16-tiered chip laminated structureobtained by cutting the semiconductor device along line B-B of FIG. 54;FIG. 57 is a back side back view illustrating the structure of thesemiconductor device in FIG. 54 on the back surface side with a sealingbody seen through. FIG. 58 is a sectional view illustrating an exampleof an eight-tiered chip laminated structure obtained by cutting thesemiconductor device along line A-A of FIG. 54; FIG. 59 is a sectionalview illustrating an example of the eight-tiered chip laminatedstructure obtained by cutting the semiconductor device along line B-B ofFIG. 54; FIG. 60 is a sectional view illustrating an example of afour-tiered chip laminated structure obtained by cutting thesemiconductor device along line A-A of FIG. 54; and FIG. 61 is asectional view illustrating an example of the four-tiered chip laminatedstructure obtained by cutting the semiconductor device along line B-B ofFIG. 54.

The semiconductor device in the second modification illustrated in FIG.54 is a frame-type semiconductor package 26 assembled using a lead frame(base material). The semiconductor device includes: multiplesemiconductor chips (first semiconductor chip 4, second semiconductorchip 5, third semiconductor chip 6, and fourth semiconductor chip 7)laminated over one surface (one side) of a lead (wiring pattern); innerleads 28 a as wiring patterns and outer leads 28 b that are connectedthereto and become external terminals; and multiple wires 2 that jointogether the electrodes of each semiconductor chip and the inner leads28 a. As illustrated in FIG. 57, further, multiple coupling leads 28 cthat respectively couple together the inner leads 28 a arranged on bothsides of the laminated semiconductor chips are arranged under the chips.The semiconductor chips, inner leads 28 a, coupling leads 28 c, andwires 2 are sealed with a sealing body 10.

The frame-type semiconductor package 26 a illustrated in FIG. 55 andFIG. 56 has a structure in which semiconductor chips are laminated in 16tiers in total by four tiers with the lamination direction changed by180 degrees at every four tiers.

The frame-type semiconductor package 26 b illustrated in FIG. 58 andFIG. 59 has a structure in which semiconductor chips are laminated ineight tiers in total by four tiers with the lamination direction changedby 180 degrees only once at the fifth tier.

The frame-type semiconductor package 26 c illustrated in FIG. 60 andFIG. 61 has a structure in which semiconductor chips are laminated infour tiers.

(Third Modification)

Description will be given to the third modification.

FIG. 62 is a perspective view illustrating an example of the structureof a semiconductor device in the third modification (both-side mounting)to the second embodiment of the invention with a sealing body seenthrough; FIG. 63 is a sectional view illustrating an example of a16-tiered chip laminated structure obtained by cutting the semiconductordevice along line A-A of FIG. 62; FIG. 64 is a sectional viewillustrating an example of the 16-tiered chip laminated structureobtained by cutting the semiconductor device along line B-B of FIG. 62;FIG. 65 is a sectional view illustrating an eight-tiered chip laminatedstructure obtained by cutting the semiconductor device along line A-A ofFIG. 62; and FIG. 66 is a sectional view illustrating an example of theeight-tiered chip laminated structure obtained by cutting thesemiconductor device along line B-B of FIG. 62.

The semiconductor device in the third modification illustrated in FIG.62 is a frame-type semiconductor package 27 assembled using a leadframe. The semiconductor device includes: multiple semiconductor chipslaminated on both sides of a lead (wiring pattern); inner leads 28 a aswiring patterns and outer leads 28 b that are connected thereto andbecome external terminals; and multiple wires 2 that join together theelectrodes of each semiconductor chip and the inner leads 28 a.

The frame-type semiconductor package 27 a illustrated in FIG. 63 andFIG. 64 has a structure in which the following measure is taken: on oneside of the lead, semiconductor chips are laminated in eight tiers byfour tiers with the lamination direction changed only once by 180degrees at the fifth tier. This structure is formed on both sides of thesemiconductor package. That is, the 16 semiconductor chips (firstsemiconductor chips 4, second semiconductor chips 5, third semiconductorchips 6, and fourth semiconductor chips 7) are placed over the couplingleads 28 c on both sides.

The frame-type semiconductor package 27 b illustrated in FIG. 65 andFIG. 66 has a structure in which semiconductor chips are laminated infour tiers on one side. This structure is formed on both sides. That is,the eight semiconductor chips (first semiconductor chips 4, secondsemiconductor chips 5) are placed over the coupling leads 28 c on bothsides.

In these frame-type semiconductor packages 26 a, 26 b, 26 c, 27 a, 27 b,the coupling leads 28 c as multiple independent wiring patterns arerouted under the chips as illustrated in FIG. 56, FIG. 57, FIG. 59, FIG.61, FIG. 64, and FIG. 66. It is difficult to enhance the flatness in theindependent coupling leads 28 c.

To cope with this, a combination of the thick-type first semiconductorchip 4 and the thick first adhesive layer 8 is used as the semiconductorchip in the lowermost tier joined to the multiple coupling leads 28 c.As a result, unevenness arising from the independent coupling leads 28 ccan be absorbed.

A combination of the thick-type first semiconductor chip 4 (or thirdsemiconductor chip 6) and the thick first adhesive layer 8 is used inthe lowermost tier, the first tier after a turn-back, and the uppermosttier as in the LGA 1 in the first embodiment. As a result, the effect ofensuring the strength of the chips themselves and ensuring the height ofsteps can be obtained.

A combination of the thin-type second semiconductor chip 5 (or fourthsemiconductor chip 7) and the thin second adhesive layer 9 is used inthe tiers other than the lowermost tier, the first tier after aturn-back, and the uppermost tier. As a result, the effect of reductionin the thickness of the semiconductor device can be obtained as in theLGA 1.

(Fourth Modification)

In the description of the first embodiment, the LGA 1 has been taken asan example of the semiconductor device. However, the semiconductordevice need not be LGA 1 and may be BGA (Ball Grid Array) or the like inwhich thin-type semiconductor chips are placed over a wiring board 3 asa base material.

(Fifth Modification)

In the description of the first embodiment, a case where the followingmeasure is taken to absorb unevenness arising from a wiring pattern orthe like, formed in the upper surface 3 a of the wiring board 3 has beentaken as an example: a combination of the thick-type first semiconductorchip 4 and the thick first adhesive layer 8 is used. When the flatnessof the upper surface 3 a of the wiring board 3 is ensured, a combinationof the thin-type semiconductor chip and the thin adhesive layer may beused for the semiconductor chip in the lowermost tier. In this case, themultiple-tiered chip lamination has the following configuration: aconfiguration in which the first, second, fourth semiconductor chips areof thin-type and only the third semiconductor chip is thicker than thefirst, second, and fourth semiconductor chips.

(Sixth Modification)

In the description of the first and second embodiments, cases where thefollowing measure is taken have been taken as examples: the thickness ofthe adhesive layer formed over the back surface 4 d of the firstsemiconductor chip 4 having the first thickness (Tw1) is made largerthan the following thickness: the thickness of the adhesive layer formedover the back surface 5 d of the second semiconductor chip 5 having thesecond thickness (Tw2). However, the adhesive layer 9 having the secondthickness (Td2) illustrated in FIG. 6 may be used as the adhesive layerformed over the semiconductor chip in, for example, the fifth tier aslong as the following condition is met: the thickness of the firstsemiconductor chip 4 used as the semiconductor chip in the fifth tiershould be sufficient to prevent contact between a wire joined to thesemiconductor chip in the fourth tier and the semiconductor chip in thesixth tier. This makes it possible to reduce the thickness of thesemiconductor device (LGA) 1.

The invention is suitable for assembling an electronic device formed bylaminating thin-type semiconductor chips.

1. A method of manufacturing a semiconductor device, comprising thesteps of: (a) providing a base material having an upper surface and alower surface opposite to the upper surface; (b) after the step (a),arranging a first semiconductor chip having a first front surface, aplurality of first bonding pads formed on the first front surface, and afirst back surface opposite to the first front surface over the uppersurface of the base material; and (c) after the step (b), arranging asecond semiconductor chip having a second front surface, a plurality ofsecond bonding pads formed on the second front surface, and a secondback surface opposite to the second front surface over the firstsemiconductor chip such that the first bonding pads are exposed from thesecond semiconductor chip, wherein the first and second semiconductorchips are acquired by the steps of: (d1) providing a semiconductor waferformed in a round in planar shape and having a reference portion formedtherein; and (d2) in dicing in a first direction along a first straightline coupling the reference portion and the center point of thesemiconductor wafer, advancing a blade from a first point in a firstportion of the side of the semiconductor wafer toward a second pointpositioned in a second portion of the side and opposed to the firstpoint with a second straight line in between in the first direction, thesecond straight line being orthogonal to the first straight line andrunning through the center point of the semiconductor wafer.
 2. Themethod of manufacturing a semiconductor device, according to claim 1,wherein the thickness of the first semiconductor chip is larger than thethickness of the second semiconductor chip.
 3. The method ofmanufacturing a semiconductor device, according to claim 2, wherein aplurality of wiring patterns are formed in an area of the base materialplanarly overlapping with the first semiconductor chip.
 4. The method ofmanufacturing a semiconductor device, according to claim 1, wherein thefirst semiconductor chip is fixed over the upper surface of the basematerial through a first adhesive layer, wherein the secondsemiconductor chip is fixed over the first semiconductor chip through asecond adhesive layer, and wherein the thickness of the first adhesivelayer is larger than the thickness of the second adhesive layer.
 5. Amethod of manufacturing a semiconductor device, comprising the steps of:(a) providing a base material having an upper surface quadrilateral inplanar shape, a plurality of first bonding leads formed along a firstboard side of the upper surface, a plurality of second bonding leadsformed along a second board side opposed to the first board side, and alower surface opposite to the upper surface; (b) after the step (a),arranging a first semiconductor chip having a first front surfacequadrilateral in planar shape, a plurality of first bonding pads formedalong a first chip side of the first front surface, and a first backsurface opposite to the first front surface over the upper surface ofthe base material so that the distance between the first chip side andthe first board side is smaller than the distance between the first chipside and the second board side in a plan view; (c) arranging a secondsemiconductor chip having a second front surface quadrilateral in planarshape, a plurality of second bonding pads formed along a second chipside of the second front surface, and a second back surface opposite tothe second front surface over the first semiconductor chip such that thedistance between the second chip side and the first board side issmaller than the distance between the second chip side and the secondboard side in the plan view and the first bonding pads are exposed fromthe second semiconductor chip; (d) respectively electrically couplingthe first bonding leads to the first bonding pads via a plurality offirst wires; (e) respectively electrically coupling the first bondingpads to the second bonding pads via a plurality of second wires; (f)after the step (e), arranging a third semiconductor chip having a thirdfront surface quadrilateral in planar shape, a plurality of thirdbonding pads formed along a third chip side of the third front surface,and a third back surface opposite to the third front surface over thesecond semiconductor chip such that the distance between the third chipside and the second board side is shorter than the distance between thethird chip side and the first board side in the plan view and the secondbonding pads are exposed from the third semiconductor chip; (g)arranging a fourth semiconductor chip having a fourth front surfacequadrilateral in planar shape, a plurality of fourth bonding pads formedalong a fourth chip side of the fourth front surface, and a fourth backsurface opposite to the fourth front surface over the thirdsemiconductor chip so that the distance between the fourth chip side andthe second board side is smaller than the distance between the fourthchip side and the first board side in the plan view, substantially theentire surface of the second semiconductor chip is covered with thefourth semiconductor chip in the plan view, and the third bonding padsare exposed from the fourth semiconductor chip; (h) respectivelyelectrically coupling the second bonding leads to the third bonding padsvia a plurality of third wires; and (i) respectively electricallycoupling the third bonding pads to the fourth bonding pads via aplurality of fourth wires; the step (d) including the steps of: (j1)forming a first bump electrode in one of the first bonding pads; (j2)after the step (j1), joining a ball portion of the first wire to one ofthe first bonding leads using a capillary; (j3) after the step (j2),joining part of the first wire to the front surface of the first bumpelectrode, wherein at the step (j1), the apical surface of the capillaryis pressed against the front surface of the first bump electrode to formin the front surface of the first bump electrode an inclined plane whoseheight is reduced from the central part of the first front surface ofthe first semiconductor chip toward the first chip side, wherein at thestep (j3), the part of the first wire is joined to the inclined plane,the step (e) including the steps of: (i1) forming a second bumpelectrode in one of the second bonding pads; (i2) after the step (i1),joining a ball portion of the second wire to the part of the first wireformed over one of the first bonding pads using the capillary; (i3)after the step (i2), joining part of the second wire to the frontsurface of the second bump electrode, wherein at the step (i1), theapical surface of the capillary is pressed against the front surface ofthe second bump electrode to form in the front surface of the secondbump electrode an inclined plane whose height is reduced from thecentral part of the second front surface of the second semiconductorchip toward the second chip side, and wherein at the step (i3), the partof the second wire is joined to the inclined plane.
 6. The method ofmanufacturing a semiconductor device, according to claim 5, whereinafter the step (j3), the first wire has a first portion and a secondportion positioned closer to the first chip side than the first portionis and larger in thickness than the first portion, and wherein at thestep (e), the ball portion of the second wire is joined to the firstbump electrode so that the ball portion of the second wire is broughtinto contact both with the first portion of and with the second portionof the first wire.
 7. The method of manufacturing a semiconductordevice, according to claim 6, wherein at the step (e), the ball portionof the second wire is joined to the first bump electrode so that thecentral part of the ball portion of the second wire overlaps with thecentral part of the first bump electrode in the plan view.
 8. The methodof manufacturing a semiconductor device, according to claim 7, whereinat the step (e), the ball portion of the second wire is joined to thefirst bump electrode under the guidance of the capillary, the capillaryis thereafter returned once toward the first bonding pad along a seconddirection connecting the first bonding pad and the second bonding pad onthe way from the first bonding pad to the second bonding pad, thecapillary is thereafter cut back toward the second bonding pad in acontinuous action to form a curved point in the second wire, and thenpart of the second wire is joined to the front surface of the secondbump electrode formed over the second bonding pad.
 9. The method ofmanufacturing a semiconductor device, according to claim 5, wherein thethickness of the third semiconductor chip is larger than the thicknessof each of the second and fourth semiconductor chips.